Another vote for fueling, and IME you don't have to bonk to be having trouble with it. I experience inadequate fueling as muscle fatigue, not as hunger. It actually took me a whole season to figure it out, and when I did, it was by accident, when I noticed how much stronger I rode when I'd had a big meal of brown rice an hour before the ride.

Climbing hills takes a little technique, too - learning when and how to shift and where your most efficient cadence (RPM) is on various grades.

The steering thing - hard to tell without looking at the bike and at you on it. It might just be the bike has more responsive geometry than bikes you've ridden in the past. If that's the case, you'll get used to it. But it might be a fit thing, and it might be mechanical, too. If you have a friend who knows a thing or two about bikes, you might could get their opinion.

Anyway, welcome to TE!