Weights. Start with BodyPump classes. You won't learn much but you'll get reps and some tone. Then get into a 5x5 routine (StrongLifts) and study form, a lot. I use an app for that since I don't want to think about rest pauses, reps, levels, ... I can mentally forget all that mechanical stuff and just think about form.

I'm not a personal trainer fan.

Squats. Ass to grass paused squats. Everything got better when I started getting serious about squats.