[Android Q&A, Help & Troubleshooting] deathgaze2497:
ok so i used this link to root my phone with king root http://techbeasts.com/root-galaxy-express-3-j120a/

Required downloads:

Download and install Samsung USB drivers

Download and extract Odin 3.11.1 on your computer’s desktop

Download boot image for your phone: ENG_BOOT_J120A_PG1

Download KingRoot and Super SUME APK files. Extract the folder and copy the APKs to your phone’s internal storage.

How to flash boot image to make the phone root-able

Open Odin.exe from the extracted Odin files you downloaded on your computer’s desktop.

In Odin, click the “AP” tab in Odin and select the ENG_BOOT_J120A_PC1.tar for your device that you just downloaded above.

The only options checked in Odin should be Auto Reboot and F.Reset Time. No other options should be ticked.

Now put your phone in download mode. Turn it off first. Now press and hold Volume Down + Home + Power buttons. As soon as it boots up, leave the keys. Once it shows warning, press Volume Up to continue.

Connect your phone to your PC while Odin is open.

Once your the ID:COM box turns blue in Odin after the successful connection, click the Start button.

It will flash the boot image file and reboot the phone now.

Install Kingroot

Now on your phone, go to settings > security > allow unknown sources.

Open a file manager and locate the copied Kingroot APK file.

Tap the Kingroot APK file and install it.

Once installed, open Kingroot from the app drawer.

Tap the Android Icon on the screen shown in Kingroot or if it’s already processing, let it do that.

Kingroot will start finding an exploit to root your device now. As soon as it finds an exploit, it will root and reboot your device.

Replace King User with SuperSU

Install Super SUME APK just the way you installed Kingroot.

Open Super SUME from the App Drawer now.

Follow the instructions on-screen to finish the Super SUME procedure.

Super SUME will begin to uninstall Kingroot in favour of SuperSU now.

After uninstalling KingRoot it will install SuperSU.

SuperSU will appear in app drawer after installion. That’s all.

NOTE: sometimes when u flash the ENG_BOOT_J120A_PG1 file to get root with king root it wont work try rebooting trying again or flashing file again with odin i had to flash 3 times in some cases.

READ ALL BEFORE TRYING ROOT IMPORTANT!

and after i got king root to root my phone through this method i had to downlaod a different copy of supersu me pro from i think this link https://apkpure.com/super-sume/darkslide.com.supersume if its not the right one then just google a pro copy apk but yea so once super user is done with king root and u have a copy of supersu me pro that works just run it u may have to do it a few times and it may act funny or seem to pause half way through the root process but if it dose (like it did on mine) just have supersu app installed and run it while supersu me pro is running and it should install sucessfully keep trying till it dose thats what i did oh btw when u get super user with king root download link to sd and freeze all these apps ok (scrole down)

bbcagent

com.sec.enterprise.knox.attestation

device protection manager

diagmonagent

easy setup

elm agent

galaxy apps

klms agent

knox

knox setup wizard client

knox apps update agent

knox folder container

lookout security

new registration

personal data managnmment

rcpcomponents

remote controles

rootpa

samsungdlp services

security policy updates

security log agent

setup & transfer

spftware update

usage manager

att adress book sync

at&t locker

at&t navigator

at&t protect plus

at&t smart wifi

at&t software update

callername id

and keep runing supersu me pro and supersu me untill it installes root succesfully that worked for me

also i JUST got viper4android to work with samsung galaxy express 3 btw fallow the guide in this video https://www.youtube.com/watch?v=nFqbz8Ytjx0 and download the files from the mega link in description of video.

and now i have supersu and viper4android NOTE: be sure to have installed bussybox before trying to install viper its needed i got my bussybox from fdroid.

also if u want to get xposed modules working download an app called flashfire i think 0.53 is the latest once u have root with supersu and download and install xposed framework wanam 20161128 and flash the zip with flash fire and a side note the newest copy of gltools also works with driver support i havent had a single problem with gltools. if ur system ui crashes after boot eather keep rebooting untill it stops crashing or unsinstall an app u may think caused the issue or unfreeze an app that may be causeing it dont freeze apps unless u think its safe do it at ur own risk and freeze only apps i have found to be frozen with little to no problems. as far as xposed modules go lucky patcher installs but dosent work right due to not being on a custom rom and device id changer free works fine and xinternal sd works great and xprivacy works great and android n ify works great also gravity box for 6.0 marshmallow works fine but i only used it to make volume buttons switch tracks and for a battery bar i recomend not useing it for anything else as it has caused my phone to freeze and crash and bootloop so if u want a battery bar and to change tracks on lock screen use gravity box if u dont need those things then dont use it at all or at ur own risk.

so now u have viper and xposed and supersu enjoy it has been a pain in my ass for a long time so have fun. NOTE: there is no custom recovery for this phone sometimes when u flash these files the phone will bootloop but TRUST ME if it boot loops take the battery out and turn it back on untill it turns on sometimes doing this will force the phone to clear dalvic catch i think because it upgrades all the android apps again so keep removing the battery if it dosent work after about 20 tries the reflash ur stock rom with odin just download a stock rom from google for this device and flash all files ap=ap etc... hope this all helps