Start castling to protect your king, develop all of your pieces instead of moving one or two and using the rest as sacrifices, control the center of the board with a solid pawn structure to prevent attacks.
Mainly, work on your defense and only make trades when it benefits your overall position.
Learn and apply the most important principles of chess. - (core of my teaching) Always blunder-check your moves. Solve tactics in the right way. Analyze your games. Study games of strong players. Learn how to be more psychologically resilient. Work on your time management skills. Get a coach if you can.