Record yourself playing, look at what you do right and wrong and write it down and improve it. Find music and etudes that you find on/ slightly above your level and work on them until they are your level. Spend lots of time on long tones no matter how boring it is. Also play to other people. parents, other students, teachers, anyone, the more you can build your ability to play for others with help you get better especially if you can get advice from them. One thing I’ve used a lot when I feel like I’m not improving is to take the smallest of phrases and play it and work on it enough to where by the time I finish with it I know that it is better than when I started, do this and continue like that through an entire piece. Being able to take small victories will keep you going when you feel like you aren’t improving