you play too nit, 19/15 are stats of a nit playing full ring, you play 6max. open up you're range because I think this is where you are loosing value. play all pocket pairs, AT+, KJ+, QJ+, and suited connectors from 45s+.
ofc you will need to learn when and against who to play some of these hands because not all these hands play well against everyone. there are plenty of factors that come in to play like position, stacks, stats and others.
and definitely put more hours in to studying than in to playing and your win rate will improve.