For endgames I recommend Silman's Complete Endgame Course.
For the middle game, practice a lot, and do a lot of chess problems (there are apps that contain thousands of tactical chess problems).
After a while you will start to see how the opening leads into the midgame leads into the endgame.
As far as videos, ChessNetwork on YouTube is a great channel and the guy who runs it offers great insight and plays a LOT.
For endgames I recommend Silman's Complete Endgame Course.
For the middle game, practice a lot, and do a lot of chess problems (there are apps that contain thousands of tactical chess problems).
After a while you will start to see how the opening leads into the midgame leads into the endgame.
As far as videos, ChessNetwork on YouTube is a great channel and the guy who runs it offers great insight and plays a LOT.