So I want to get to my Uni by bicycling on a dedicated bike trail

>>1102328
I'd be more concerned about the height of the saddle; since you're learning, put the saddle at a height where you can comfortably (leg nearly fully extended) place your feet flat on the floor.

You'll be able to retrain your brain to ride a bike again.
There's no real 'guide' to learning how to ride, since it's basically keep trying until you get it. I recommend learning somewhere soft so when you fall over (and you will fall over) it's not so bad.
Practice over and over again.

>>1102328
Find a small hill, like a 1% inclination or less, and try maintaining your equilibrium. Do as >>1102573
said and lower your saddle so that you can stop with your foot. There's no good position nor height for the handlebar, it depend on your flexibility. You can go to a lbs after you mastered the way of the bike to get a pro fit.

>>1102328
Why don't you get a trike?

>>1102328
they sell tricycles with big baskets between the rear wheels, so you look like a grocery delivery dude and not adult who cant ride bike