endgame learning?

Endgames are tough, but you can learn to handle them effectively by starting with the basics -- mate with K+Q vs K, mate with K+R vs K, K+P vs K, etc -- then moving on to a bit more complex endings followed by endgame strategy. The best resource that I know of for this type of graduated learning is Silman's "Complete Endgame Course". It starts with the basics and builds from there.

If you don't want to get Silman's book, you should still learn endgames by starting with the basics and working up from there. There are many online resources for doing that. The only problem is deciding what should be studied first, and what should follow. If there is a chess club near you, it might be possible to find a strong player who is willing to help you work through the progression.

I wish you all the best in your chess endeavors.

Your problem is not end game, it is time control.   You are playing blitz & bullet, time controls that are too fast for inexperienced players.  Play slower controls to work on making good moves,  avoid hanging pieces, piece development and combination piece play. Do self-analysis of each game, win or loss.  Play less, study more.  Master these and your rating will significantly improve.

Fast games teach you how to make mistakes  faster, which in turn creates bad habits.

:)