The only way to get better at riding is to ride.

I'd suggest doing more recreational riding on paths or trails, or even parking lots, until you build up the confidence in your bike-handling skills to negotiate traffic.

As for fit, if it feels wrong, it probably is. Were you fitted by a bike shop for this bike? If not, considering taking it into one and getting a fit.

A typical rule of thumb for saddle height is to raise it up until your knee is just slightly bent (no more than 15 degrees) when your pedal is at the bottom of its stroke.

Lots of people have difficulty mounting & dismounting even when the bike fits right. Are you able to stand over the top bar with both feet on the ground? Do that, then step on one pedal to get going and lift yourself into the saddle with the same movement. To dismount, reverse this procedure.

See www.sheldonbrown.com for lots more advice on basic bike-handling and fit.