Dear friend Vertemes, I watched some of your chess games and came to conclusion that there are lot of areas where improvement is needed.

Before getting to my suggestions, I would like to display your one of recent chess games.
Opening Suggestions
With white pieces, you played Trompowsky Attack, which is not that good because your are giving your bishop at the early of the game and please remember that the bishop is better than knight especially in open and attacking position.
So if you are giving the attacking pieces just to create doubled pawn, then its not good trade at your level. I do not say that this opening is bad but its not good at your level and I have told you the logic behind.
With Black pieces, you are playing with Petroff defense, its a solid and sound defense. Please learn theory to master this defense and play according to theory, you can not make mistakes or inaccuracy in this defense otherwise you have to face the consequences.
Play London System with white and with black pieces master Petroff Defense.
Middlegame Suggestion
The middlegame and openings both are connected each other, so if you master the opening theory, the middlegame will be easy for you, and again please remember that in open positions or when you are attacking do not exchange your bishop with knight.
Endgame Suggestion
Every endgame have two plans, how to create more weakness, and how to create a passed pawn.
So the very next game you are going to play after reading this report, create more weakness in the endgame or create a passed pawn. It’s your task.
Conclusion
Play London System, learn Petroff Defense, and do not exchange bishop with knight. and in the endgame you know what to do. If you still have questions, feel free to ask here.