You are a professional PineScript version=5 developer.
You know how to code indicators and strategies and you also know their differences in code.
I need your help to improve this TradingView strategy please.

Add this indicator to this strategy and remove the plots and fills it has:
//@version=4
study("Supertrend", overlay = true, format=format.price, precision=2, resolution="")

Periods = input(title="ATR Period", type=input.integer, defval=10)
src = input(hl2, title="Source")
Multiplier = input(title="ATR Multiplier", type=input.float, step=0.1, defval=3.0)
changeATR= input(title="Change ATR Calculation Method ?", type=input.bool, defval=true)
showsignals = input(title="Show Buy/Sell Signals ?", type=input.bool, defval=true)
highlighting = input(title="Highlighter On/Off ?", type=input.bool, defval=true)
atr2 = sma(tr, Periods)
atr= changeATR ? atr(Periods) : atr2
up=src-(Multiplier*atr)
up1 = nz(up[1],up)
up := close[1] > up1 ? max(up,up1) : up
dn=src+(Multiplier*atr)
dn1 = nz(dn[1], dn)
dn := close[1] < dn1 ? min(dn, dn1) : dn
trend = 1
trend := nz(trend[1], trend)
trend := trend == -1 and close > dn1 ? 1 : trend == 1 and close < up1 ? -1 : trend
upPlot = plot(trend == 1 ? up : na, title="Up Trend", style=plot.style_linebr, linewidth=2, color=color.green)
buySignal = trend == 1 and trend[1] == -1
plotshape(buySignal ? up : na, title="UpTrend Begins", location=location.absolute, style=shape.circle, size=size.tiny, color=color.green, transp=0)
plotshape(buySignal and showsignals ? up : na, title="Buy", text="Buy", location=location.absolute, style=shape.labelup, size=size.tiny, color=color.green, textcolor=color.white, transp=0)
dnPlot = plot(trend == 1 ? na : dn, title="Down Trend", style=plot.style_linebr, linewidth=2, color=color.red)
sellSignal = trend == -1 and trend[1] == 1
plotshape(sellSignal ? dn : na, title="DownTrend Begins", location=location.absolute, style=shape.circle, size=size.tiny, color=color.red, transp=0)
plotshape(sellSignal and showsignals ? dn : na, title="Sell", text="Sell", location=location.absolute, style=shape.labeldown, size=size.tiny, color=color.red, textcolor=color.white, transp=0)
mPlot = plot(ohlc4, title="", style=plot.style_circles, linewidth=0)
longFillColor = highlighting ? (trend == 1 ? color.green : color.white) : color.white
shortFillColor = highlighting ? (trend == -1 ? color.red : color.white) : color.white
fill(mPlot, upPlot, title="UpTrend Highligter", color=longFillColor)
fill(mPlot, dnPlot, title="DownTrend Highligter", color=shortFillColor)
alertcondition(buySignal, title="SuperTrend Buy", message="SuperTrend Buy!")
alertcondition(sellSignal, title="SuperTrend Sell", message="SuperTrend Sell!")
changeCond = trend != trend[1]
alertcondition(changeCond, title="SuperTrend Direction Change", message="SuperTrend has changed direction!")

Now improve the strategy like so:
- Open long position as soon as the gaussian channel is green, the close price is above the high gaussian channel band and when the Stochastic RSI is above 80 or below 20.
- Close long positions when the close price crosses the high gaussian channel band to the downside.

Respect these instructions:
- For the indicator we are adding, preserve the timeframe logic it has if there is one, fill gaps whenever possible.
- Keep all existing plots & visuals (don't remove them).
- Don't trigger a short. Simply go Long and Flat.
- Always use 100% of capital.
- Set commission to 0.1%.
- Set slippage to 3.
- strategy.commission.percent and strategy.slippage don't exist in PineScript. Please avoid this mistake. Set those variables in the strategy() function when initiating the strategy.
- When initiating the strategy() function, don't use line breaks as this will cause a compiler error.
- Leave all other strategy settings to default values (aka. don't set them at all).
- Add Start Date and End Date inputs/filters so the user can choose from when to when to execute trades. Start with 1st January 2018 and go to 31st December 2069.
- When setting the title of the strategy, add "Demo GPT - " at the start of the name and then continue with the name of the strategy.

This is the code of the TradingView Strategy to improve with the instructions above:
//@version=5
strategy(title="Gaussian Channel Strategy v3.0", overlay=true, calc_on_every_tick=false, initial_capital=1000, default_qty_type=strategy.percent_of_equity, default_qty_value=100, commission_type=strategy.commission.percent, commission_value=0.1, slippage=3, fill_orders_on_standard_ohlc=true)

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
// Gaussian Channel Indicator - courtesy of @DonovanWall
//----------------------------------------------------------------------------------------------------------------------------------------------------------------- 

// Date condition inputs
startDate = input.time(timestamp("1 January 2018 00:00 +0000"), "Start Date", group="Main Algo Settings")
endDate = input.time(timestamp("31 Dec 2069 23:59 +0000"), "End Date", group="Main Algo Settings")
timeCondition = time >= startDate and time <= endDate

// This study is an experiment utilizing the Ehlers Gaussian Filter technique combined with lag reduction techniques and true range to analyze trend activity.
// Gaussian filters, as Ehlers explains it, are simply exponential moving averages applied multiple times.
// First, beta and alpha are calculated based on the sampling period and number of poles specified. The maximum number of poles available in this script is 9.
// Next, the data being analyzed is given a truncation option for reduced lag, which can be enabled with "Reduced Lag Mode".
// Then the alpha and source values are used to calculate the filter and filtered true range of the dataset.
// Filtered true range with a specified multiplier is then added to and subtracted from the filter, generating a channel.
// Lastly, a one pole filter with a N pole alpha is averaged with the filter to generate a faster filter, which can be enabled with "Fast Response Mode". 

// Custom bar colors are included.

// Note: Both the sampling period and number of poles directly affect how much lag the indicator has, and how smooth the output is.
//      Larger inputs will result in smoother outputs with increased lag, and smaller inputs will have noisier outputs with reduced lag.
//      For the best results, I recommend not setting the sampling period any lower than the number of poles + 1. Going lower truncates the equation.

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
// Updates:
// Huge shoutout to @e2e4mfck for taking the time to improve the calculation method!
// -> migrated to v4
// -> pi is now calculated using trig identities rather than being explicitly defined.
// -> The filter calculations are now organized into functions rather than being individually defined.
// -> Revamped color scheme.

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
// Functions - courtesy of @e2e4mfck
//----------------------------------------------------------------------------------------------------------------------------------------------------------------- 

// Filter function 
f_filt9x (_a, _s, _i) => 
    int _m2 = 0, int _m3 = 0, int _m4 = 0, int _m5 = 0, int _m6 = 0, 
    int _m7 = 0, int _m8 = 0, int _m9 = 0, float _f = .0, _x = (1 - _a)
    // Weights. 
    // Initial weight _m1 is a pole number and equal to _i
    _m2 := _i == 9 ? 36  : _i == 8 ? 28 : _i == 7 ? 21 : _i == 6 ? 15 : _i == 5 ? 10 : _i == 4 ? 6 : _i == 3 ? 3 : _i == 2 ? 1 : 0
    _m3 := _i == 9 ? 84  : _i == 8 ? 56 : _i == 7 ? 35 : _i == 6 ? 20 : _i == 5 ? 10 : _i == 4 ? 4 : _i == 3 ? 1 : 0
    _m4 := _i == 9 ? 126 : _i == 8 ? 70 : _i == 7 ? 35 : _i == 6 ? 15 : _i == 5 ? 5  : _i == 4 ? 1 : 0
    _m5 := _i == 9 ? 126 : _i == 8 ? 56 : _i == 7 ? 21 : _i == 6 ? 6  : _i == 5 ? 1  : 0 
    _m6 := _i == 9 ? 84  : _i == 8 ? 28 : _i == 7 ? 7  : _i == 6 ? 1  : 0 
    _m7 := _i == 9 ? 36  : _i == 8 ? 8  : _i == 7 ? 1  : 0 
    _m8 := _i == 9 ? 9   : _i == 8 ? 1  : 0 
    _m9 := _i == 9 ? 1   : 0
    // filter
    _f :=   math.pow(_a, _i) * nz(_s) + 
      _i  *     _x      * nz(_f[1])      - (_i >= 2 ? 
      _m2 * math.pow(_x, 2)  * nz(_f[2]) : 0) + (_i >= 3 ? 
      _m3 * math.pow(_x, 3)  * nz(_f[3]) : 0) - (_i >= 4 ? 
      _m4 * math.pow(_x, 4)  * nz(_f[4]) : 0) + (_i >= 5 ? 
      _m5 * math.pow(_x, 5)  * nz(_f[5]) : 0) - (_i >= 6 ? 
      _m6 * math.pow(_x, 6)  * nz(_f[6]) : 0) + (_i >= 7 ? 
      _m7 * math.pow(_x, 7)  * nz(_f[7]) : 0) - (_i >= 8 ? 
      _m8 * math.pow(_x, 8)  * nz(_f[8]) : 0) + (_i == 9 ? 
      _m9 * math.pow(_x, 9)  * nz(_f[9]) : 0)

// 9 var declaration fun
f_pole (_a, _s, _i) =>
    _f1 =            f_filt9x(_a, _s, 1),      _f2 = (_i >= 2 ? f_filt9x(_a, _s, 2) : 0), _f3 = (_i >= 3 ? f_filt9x(_a, _s, 3) : 0)
    _f4 = (_i >= 4 ? f_filt9x(_a, _s, 4) : 0), _f5 = (_i >= 5 ? f_filt9x(_a, _s, 5) : 0), _f6 = (_i >= 6 ? f_filt9x(_a, _s, 6) : 0)
    _f7 = (_i >= 2 ? f_filt9x(_a, _s, 7) : 0), _f8 = (_i >= 8 ? f_filt9x(_a, _s, 8) : 0), _f9 = (_i == 9 ? f_filt9x(_a, _s, 9) : 0)
    _fn = _i == 1 ? _f1 : _i == 2 ? _f2 : _i == 3 ? _f3 :
      _i == 4     ? _f4 : _i == 5 ? _f5 : _i == 6 ? _f6 :
      _i == 7     ? _f7 : _i == 8 ? _f8 : _i == 9 ? _f9 : na
    [_fn, _f1]

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
// Inputs
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------

// Source
src = input(defval=hlc3, title="Source")

// Poles
int N = input.int(defval=4, title="Poles", minval=1, maxval=9)

// Period
int per = input.int(defval=144, title="Sampling Period", minval=2)

// True Range Multiplier
float mult = input.float(defval=1.414, title="Filtered True Range Multiplier", minval=0)

// Lag Reduction
bool modeLag  = input.bool(defval=false, title="Reduced Lag Mode")
bool modeFast = input.bool(defval=false, title="Fast Response Mode")

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
// Definitions
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------

// Beta and Alpha Components
beta  = (1 - math.cos(4*math.asin(1)/per)) / (math.pow(1.414, 2/N) - 1)
alpha = - beta + math.sqrt(math.pow(beta, 2) + 2*beta)

// Lag
lag = (per - 1)/(2*N)

// Data
srcdata = modeLag ? src + (src - src[lag]) : src
trdata  = modeLag ? ta.tr(true) + (ta.tr(true) - ta.tr(true)[lag]) : ta.tr(true)

// Filtered Values
[filtn, filt1]     = f_pole(alpha, srcdata, N)
[filtntr, filt1tr] = f_pole(alpha, trdata,  N)

// Lag Reduction
filt   = modeFast ? (filtn + filt1)/2 : filtn
filttr = modeFast ? (filtntr + filt1tr)/2 : filtntr

// Bands
hband = filt + filttr*mult
lband = filt - filttr*mult

// Colors
color1   = #0aff68
color2   = #00752d
color3   = #ff0a5a
color4   = #990032
fcolor   = filt > filt[1] ? #0aff68 : filt < filt[1] ? #ff0a5a : #cccccc
barcolor = (src > src[1]) and (src > filt) and (src < hband) ? #0aff68 : (src > src[1]) and (src >= hband) ? #0aff1b : (src <= src[1]) and (src > filt) ? #00752d : 
           (src < src[1]) and (src < filt) and (src > lband) ? #ff0a5a : (src < src[1]) and (src <= lband) ? #ff0a11 : (src >= src[1]) and (src < filt) ? #990032 : #cccccc

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
// Outputs
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------

// Filter Plot
filtplot = plot(filt, title="Filter", color=fcolor, linewidth=3)

// Band Plots
hbandplot = plot(hband, title="Filtered True Range High Band", color=fcolor)
lbandplot = plot(lband, title="Filtered True Range Low Band", color=fcolor)

// Channel Fill
fill(hbandplot, lbandplot, title="Channel Fill", color=color.new(fcolor, 80))

// Bar Color
barcolor(barcolor)

// Trading Logic
longCondition = ta.crossover(close, hband) and timeCondition
closeAllCondition = ta.crossunder(close, hband) and timeCondition

if longCondition
    strategy.entry("long", strategy.long)

if closeAllCondition
    strategy.close("long")