Chess improving

Work on thinking process. Heisman's Improving Chess Thinker is a step in the right direction. Take the advice from his class F and below and class E sections. But before reading protocols do the given positions yourself and follow the instructions (write down your assessment, evaluation, and calculations and the evaluation after each line). Move onto the next position when you decided on a final move.
Something like this could be said, "This is very likely a Dutch since the queen usually goes to e8 in some lines and now she's on c6. Can't really see a way to exploit the pawns in front of the white king so I can't really say with confidence that mine is safer especially with pressure against e6. Ng5 looks danerous. Candidates include 1...h6 1...Ne4 1...e5 1...Qe4 (Much later in the protocol) 1...Ne4 looks best to me since it takes g5 away from the white knight, threatens a fork against the queen and rook, blunts the queen's influence over e6, and opens the f-file pressuring his knight so 1...Ne4 with a still unclear but certainly not much worse position pushes clock. "

Join the local chess club, listen to their post-mortems (analysis after a game). You learn alot from that. Study GM games with their annotations. Play chess for fun (and do the tactics, it works), and you will improve.

Keep doing tactics everyday. If you can keep up 10-30 tactics a day for 6 months you will be significantly stronger. Just make sure you take them seriously and never "guess".
Recently i passed the 1100's rating... i often beat 1250 rating.. but sometimes i lose versus 1100-1150 players.. it's normal? i started playing chess since about 4 months... it's possibile for me to become at least 2000 elo in the future? i'm 16 years old
I'm around 1320 something and I'm 14, and I have similar questions to the OP
1. Is it possible for me to go over 2000 elo?
2. And if so how?

The answer is yes. The process to learn how is
1. accomplish tactics at a 2000+ level
2. Learn how to maximize your pieces positions and restrict your opponents piece positions. Learn how to make pieces good and bad. Various intermediate level positional books will teach you this.
3. Learn a decent amount about endgame. Silman's Complete Endgame Course should give you enough knowledge to accomplish this.
4. Learn the pawn structure plans of basic opening positions. There are a lot of pawn structures and learning the plans with illustrative master games will let you understand them with work.
5. After having learned the pawn structure plans of various openings, find critical opening books for your prefered opening lines and learn how to play them. If you understand pawn structures you wont need them as much, but it helps to play the game faster if you have lines memorized, rather than spending an hour a game calculating out the opening. Chesspub.com is a good place to look at high level discussion of opening books, and maybe even here you will get good recommendations on the best opening books.
6. Study classical master games and try to predict each of their moves and understand their game plans. Knowing what you do about the pawn structures, tactics, piece positioning, and endgame you should be able to understand the majority of their moves even if you cant predict them. I dont think you can ever study too many master games.
7. Finally if you still want to continue improving look for grandmasters analyzing their own games or other grandmasters games. This will show you the thinking style of top grandmasters and how they incorporate all their knowledge into trying to win a game. The videos on chess.com I found were good for this and allowed me to gain a vastly better way of thinking about things than I had before.
Well anyways do all of these seriously to the point you truly understand them and you should be atleast expert level. I've done the majority of these things and I've beaten 2090 players in tournaments and been steadily climbing my rating up 40+ points per tournament (Im 2030 right now). I don't think I'm quite master strength, I need to just slightly improve in everything Ive listed to get there, and definitely need to study more master games.