Comment by gregjotau

I would recommend using something like tonedear.com and practicing ear training mostly. I played a lot of classical music when I was 14-15, my biggest regret is not focusing more on ear training :)

I made a (bad) video about interval recognition and how you can map to songs: https://www.youtube.com/watch?v=DILEEOybFQI

In addition to https://tonedear.com, I have used the functional ear trainer app and seen good results.