Hi, SmileShadow,
welcome, I think for improvement, you'll have to have some strategies when you're practicing, are there any that you have been using? Because the biggest time waster on the piano is to play pieces over and over again... Also, I have a student who can play pretty well, but whenever I tell her to speed up, she ends up in a mess... To be able to do this, I think you should know the piece well, getting every detail comfortable at a very slow speed, then working your way up, I'm sure there are sections you could play fast, just not all of it... so practice the difficult parts using some strategies.
I'm sorry to hear that when you learnt with your previous teacher, you felt nervous because she was very strict, you should enjoy your lessons, and acquiring skills and ways of practice from a teacher. Find a teacher who you prefer, and tell them exactly what you want to acheive from learning the piano. Don't give up, and you'll progess along nicely.
Ludwig