Advice for Improvement from 1000-1100 ?

I love chess and have been playing with my grandpa since I was young.  The past year or so I've been playing a ton of online chess.  I used to just do blitz and bullet because it was fun, and I stayed around 700-800 elo for a long time. 

I read that I should do more puzzles and play longer games, so I do that, often.  I went up to just under 1200, then now I havent gone above 1100 many times since, been about 6 months.  I practice every day with puzzles and analyze all my games, watch youtube videos (i know this isnt super important), and I also bought a chess opening book that I have used to read on the ruy lopez, italian, and sicilian a bit.  Also love fried liver / traxler

I just want to know what I'm doing wrong and why I'm not improving.  I don't blunder often, I just seem to always make some mistake.

Sorry if this is a frequently asked question, but I feel like I follow all the advice I see on other forums, so maybe theres some more advice to find?

Thank you.