Middle/End-game blatant blunders

First of all learn the principles of each stage of the game (opening, middle and endgame). In this game that you show us, your opponent made horrific blunders. It's important not to rely on those blunders or opening traps, because that doesn't help you to improve.
For the middle and endgames you can try to solve some thematic puzzles. Practising will help you to see the pieces better and to understand their potential in different type of positions. Learn the principles of middle and engame too.
If you miss tactics or you just blunder pieces, probably the time control is too short for you. Try to play in a longer time controls like 10, 15, or even 30 minutes. After some games you'll start to see the board better and make less blunders.
So, as conclusion, learn the priciples, exercise and play more games.
First of all learn the principles of each stage of the game (opening, middle and endgame). In this game that you show us, your opponent made horrific blunders. It's important not to rely on those blunders or opening traps, because that doesn't help you to improve.
For the middle and endgames you can try to solve some thematic puzzles. Practising will help you to see the pieces better and to understand their potential in different type of positions. Learn the principles of middle and engame too.
If you miss tactics or you just blunder pieces, probably the time control is too short for you. Try to play in a longer time controls like 10, 15, or even 30 minutes. After some games you'll start to see the board better and make less blunders.
So, as conclusion, learn the priciples, exercise and play more games.
Thanks, this was really helpful!