When you move the shift lever, the synchronizer speeds up or slows down the speed of the gear to aid in smooth shifting. The synchro has a friction surface which makes contact first ,matching the gears rotation and locking the sleeve's teeth into the small teeth on the side of the gear. Shifting becomes effortless. The speed in the motor is transferred through the clutch to the transmission input shaft through a selected set of gears to the output shaft, then delivered through the drive shaft to the differential and the driving wheels. Gear ratio changes change the speed that the crank moves in relation to the driveshaft.
Overdrive gears have the output shaft spinning faster than the input shaft.
Gears such as .85 are good for fuel economy, not for speed. Available gear ratios are plotted on a gear chart from the gearbox manufacturer. Skills such as heel-toe, double clutching, blipping the throttle, are used to match gear speeds on the input and output shafts for smooth shifts without lurching and grinding. Smooth shifting is something you can practice everyday in your streetcar. It should be a natural unconscious motion.