Wow! Enjoyed watching how these complicated chess matches unraveled a little by little, looked so cool!
Targeting 1400

Game #11
I am ok with the way I played the game. Not great of course as I made a a blunder while in a decent position. I'm never too comfortable when castling long, but I liked the idea of brining my rook to the d file in one move.
The Italian Game: I have personally been memorizing the theory that’s gone along with this opening and it’s great for beginners.
The Modern Defence: I usually play this after 1. d4. You might wanna consider those.
A great YouTube channel that will help you increase your chess playing is: Hanging Pawns.

Castling long is fine, but there's no urgency in putting a rook on the d-file. That file is closed, and likely to stay closed for a while.
(edit: Actually, in this case the computer says castling long is a clear error. Its preferred move (by 1.2 points) is to castle short.)
This game starts to look like a race between your kingside attack and Black's queenside attack. Three things made a difference: 1) your losing a piece on move 13. Ouch. 2) Castling long leaves the a-pawn as a weak point. A simple move that will help is to put your king on b1 (or b2, after you push the b-pawn). But even then you've got trouble once his pawn reaches b4. (edit: the computer suggests instead that you play a4 immediately - move 13. Either way, castling long is costing you a tempo.) 3) Take a look at the pawns anytime after move 23. Your a and b pawns are doing defensive work, the rest of yours are useless. Black's the opposite: his h and f pawns are shaky, but his b,c,d pawns are stabbing at your king. I'd rather be black, not just because of his extra piece but because his advanced pawn on b4 is bulletproof.
Attacking kingside was the right idea after castling long. A common strategy for that is to advance your pawns first, but never mind. Always a good idea to look for faster attacks, and we all make mistakes.
Move 13 cost you a piece, but you lost the game on move 14 when you committed to wrecking your pawn structure. You were planning to sac a piece anyway, so consider desperado moves like 14. bxh6 (maybe followed by Nf5 assuming black plays gxh immediately) - you get a pawn (maybe two!) for the bishop, you expose the enemy king, and you keep your f,g,h pawns connected so you can use them later.
PS: Yep, computer agrees: a little before move 13, the game was about even. (The computer gives you a half-point lead after move 12, but neither side was playing precisely enough for a half-point to matter.) Move 13 shifted the advantage to black (to -0.5), but move 14 cost you 5 more points!
(The computer found 14. Rxe7, which is much better than my Bxh6 idea, but my point stands: you should be looking for tempo-gaining moves rather than that passive g3.)
After move 14, you're fighting one-handed for the rest of the game, but you fought well - your rook battery on the g-file, in particular, kept you in the game. But move 25 was a bigger mistake than you seem to realize. That was basically instant death, because you left your king defenseless against an obvious looming attack. 25 Qb2 is better: attack the f6 knight while defending a2 and nearby squares.
Since you asked, 26. Kd2 is better than 26. Kd1(If 26. ...Qxa2, your queen can interpose) but I agree, it's still very grim.

Thank you @Archerirving, @Hades532, @nartreb!
I'll post another game, but lately I'm kind of stuck at the 1200-1220 level and play very poorly. As soon as I have a good loss to discuss (Not one with obvious blunders at move 9) I will post it.
In terms of openings. As suggested multiple times already, I think I will go back to e4, e5 openings. The obvious minus is that people at this level are much more aware of them than d4 (personal view). However I'm more often getting stuck mid-game in a d4 opening than an e4.

Game #12:
Quite an annoying loss - got disconnected and even though I had internet the server never reconnected me again... Anyway, I feel like I was in a winning position in the end, after him blundering his N. I saw a potential mate opportunity if he challenges my Q, but as I can't rely on that I was thinking of going for exchanges to reduce the material.
The game you posted above was a strategical loss. 5...e6 is the kind of move that makes me want to vomit. You doomed that light square bishop to passivity. Also, you took on an isolated pawn by advancing e4-e5 and undefended it at that. Your center fell apart. You had chances after that, though. You resigned up a piece and winning?

Game #13:
I was a bit intimidated by 1400 opponent which I think showed in my timidness. Also, at the end I was low on time (2:30 minutes left), so my moves weren't great to say the least.

Hi @little_guinea_pig and thanks for the review.
3. I haven't started my study against Sicilian. Trying to stick to "Italian game" and I definitely have flaws in the opening against non-e5 responses. I also have flaws against e5 responses
8. I always delay my Q-side advance, so I saw a line where you expand with a4,b4 to gain some space.
13. Agree
14. At the time it looked better If I locked the position. Also I though he would run a tactic on my badly placed bishops and rook.
22. Makes sense.
23. Hah I though I would do it the other way round
31. Rook c1 looks good. Certainly much better than the bishops sitting on the 2nd rank.

Game #14 (Black, loss, 15 | 10):
Thats quite a weak game of mine. I didn't feel comfortable from the get-go. Made a blunder early on that I've made in the past (let him skewer my R through my Q). From there I made a slow and weak attempt at attack which didn't work and I actually didn't believe it would.
"Really, I don't know what is the Q doing here."
The queen has no purpose there. You have already done well equalizing as black. A good move would be a5 to undermine his queen side. That's the stockfish move. Personally, I hate cramped positions. I would try to unwind a little with 9...Ne5.
"I've done this in the past and I should stop it."
What was your idea?
"Now, I see that removing his N at c3 would play a good role in my attack, so ba5 would be better"
What attack? You were dead lost.
It seems to me that you lack a real plan. That's the hardest part for me too. I still struggle with coming up with what to do. But you should really get a hang on losing material for no reason from one move blunders because it's very hard to improve any aspect of your game until you get a handle on that.

@MasterPatzer81
Ne5 was going through my head. a5 wasn't - but I like the idea. The Q was sort of developing move - connect the rooks.
Rab8 was to open the b file with pawn push. Obviously it's a bad idea when a simple Bishop can line them up. Also a5 does the same thing, but better.
The attack I'm talking about was exactly for that reason - cause I felt dead lost. It was a tryout.
I agree on both your points - I do lack a plan. I also consider this my second weakest point, behind giving out pieces for no reason. I guess spending some time in late parts of openings/early mid-games should prove beneficial. Any videos/articles that come to mind?
The Chessmaster Grandmaster Edition program has an academy mode w/ Josh Waitzkin ... it is an amazing piece of software that has helped me tremendously. That combined with the youtube videos....Chess Club and Scholastic Center of St Louis videos really helped me a lot. Highly recommended.

Hello, I just noticed this thread and I’ll also try to contribute to the discussions and analysis. Hope you can reach 1400 soon, op!
Hello everybody.
It's been a long time since we last met.
If folks still are unaware, here my latest book addition, "The Fine Art of Chess": https://www.amazon.com/Fine-Art-Chess-Lyudmil-Tsvetkov-ebook/dp/B07SPFTJSZ/ref=sr_1_1?keywords=fine+art+of+chess&qid=1568188697&s=books&sr=1-1
It's very similar to Irving Chernev's "Logical Chess", annotating 50 full instructive games move-by-move, but as some reviewers say, probably far better in many respects.
If you want to learn how a game proceeds logically, this is the perfect choice.
Above book provides the most complete game analysis.
And as people point out, it is very easy to learn from it.
I am sure that when people read it, they will analyse their games differently.
Evaluation is of prime importance in chess.
@Tsvetkov Aren't you the guy who claims to be stronger than stockfish? Some nut is going around plugging this laughable book and I'm just wondering if its you. I don't recall. Just how strong are you?
Yeah, it's me.
I have been beating Stockfish regularly in the past, and even have written books on this, with all the games and scores.
Officially, I used to be 2200 some 15 (!) years ago, but now I am 5 or 6 times stronger, without having competed.
Too much noise at tournaments, that's why I don't play there.
Here one review by a fellow Chess.com blogger, Novacek, who has bought and read the book, to give you some idea: https://www.chess.com/blog/novacek/book-review-the-fine-art-of-chess
If you don't believe me, you may ask him yourself.
Game #10: White, 15|10, loss
I was "idealess" for the most part of this game. One or two sparks, but that was it. Couldn't take advantage of my opponents weakened king side pawns. As a whole couldn't challenge his defense properly. Also lots of useless rook moves.