stuck at 500 elo
Blunder check before you move. Think about your move. Do not play it, but imagine it played on the board. Then check it is no blunder: does not hang any piece or pawn and does not run into checkmate. Only then play it. Sit on your hands.
Improving Your Chess - Resources for Beginners and Beyond.....
https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond