I've been using the chess.com opening database but it sucks, only includes master-level long games. Lichess has a far better one but most of the time I can't be arsed to use it, too much work to move the pieces to the correct position there, on chess.com while playing it's just available right there. Based on my stats (the paid subscription on chess.com gives pretty neat stats and analysis of played games) the openings are my strong part, endgames the weak part. I should probably read a book on endgame strategy or something.