I personally use Cheessly Which is separate from chess.com to get better at chess. Their lessons are good to start improving your chess.com rating. Chess.com also has a lesson on the site and gives you access to access which is Magnus Carlsen's teaching site 'Chessable'. All sites have free content so please check the out and improve your game today.
Do not use an external database for providing moves this is against the fair play policy for Chess.com.
Do follow the fair play policy on Chess.com.
Do use the Opening database for book openings on chess.com.