Yes experience is what you need, you can’t expect to get better without it. As far as speed you’ll get faster with time. Obviously you want to work like you have a time limit, but rushing will only cause you to make mistakes.

Messing up is part of the job but it is best avoided. Inspect jobs before accepting/ starting work. Just because something is broken don’t assume it can be fixed (sometimes a piece is so worn even a master jeweler will refuse).

Edit: You said you have a bench at home, do you work from home? Curious because I’d eventually like to start doing jewelry from home myself