Targeting 1400

I edited my answer. I meant c6. I still get confused with squares :/

 I thought that might be it. Though ...Nc4 can happen if they play b4!

@pdve Is "knight from b1 to d2 to f1 to g3" standard practice or just targeting in this position?

@Giasira Yep I know about en passant, but I considered my pawn advanced and he would recapture with his other pawn. That's why I didn't do it. Looking at it now, I could recapture and have my two pawns advance afterwards. Regarding Bb5: I will try a6, b5 to kick the Bishop away. Then I assume king-side castling would be better.

@mtashev56 yes the knight maneuver is standard in the ruy lopez. expert opinion has it that n to c3 is horrible positionally. in the ruy white often tries to get a center control.

Game #6: Black, 15|10, win:

Overview: So this game I decided to defend with Sicilian (at which I'm a complete beginner). The game went very well and it was a pretty tactical one. In this instance, I'm most curious about the opening itself and the pawn structure. Also if there was a better way to play the Nd7 situation.

VERY GOOD. No mistakes in my opinion.

I think playing e4 if you have the opportunity in the Sicilian is a very good idea. As you saw white had a very nice idea of bringing his knight to e4 and then using the pawn he got to establish on e5 as an outpost. Lukcily for you he dropped a pawn before he got that far. You would block in your DSB by playing e5 that is true, but this setup is very commonly played in systems like the Kings Indian Attack or the Kings Indian Defence. Usually you will advance your f-pawn and sooner or later you can push your e-pawn further, freeing up your bishop. I`m no positional expert but I`m going through Bobby Fischers games now and he regularily adopted setups with a  temporarily blocked fianchetto bishop to good effect. 

Game #7: Black, 15|10, loss:

I'm testing the Sicilian again. This time I think my opening was sloppy and I had no idea how to respond to white's moves. However, I felt comfortable (and with a slight lead) in mid-game, at which end I made quite a blunder. The rest of the game was somewhat training defensive play for me. I think I made more than the usual amount of mistakes/blunders at every stage of the game.

I`m doing quite a bit of study of positional chess now, so hopefully I can chime in with some advice. These observations are just general ones and I hope someone higher rated than me can correct me if I`m wrong 

1. That f6 move to strengthen your pawn structure looks to have weakened your position considerably, as you saw it gave white the opportunity to play for Ng6, also you made lots of light square weaknesses around your king, which the queen could exploit. Another observation is your bishop became a typical "bad bishop" effectively just a tall pawn with no scope. You could maybe have tried to get it to a5 where it would cut into white`s position.

2. You could have taken steel control of the only semi-open file in the position by doubling rooks on the c-file, this combined with a queen on a4 and bishop on a5 would put a lot of pressure on white. If given time you could have tried to advance your a and b pawns ahead of an attack. 

Game #8: Black, 15|10, loss:

Throughout the game I had the feeling I will lose it. Even when I was ahead. I winged the opening and was ok in mid-game. However I never felt stable in my defense.

To be honest about game 6. You're annotations doesn't make much sense to me. Let's talk about it. You're opening is called the hyper dragon. You play the sicilian, but you play g6 and bg7. This is the dragon. Because you play it the earliest as can be, it's called the hyper dragon. The most important part of the hyper dragon is the bishop on g6. This is a very strong piece, probably the strongest piece right now. In some games however, like your first game, I see you play e5 quickly. And that is a very weird and to me a bad move, because you are blocking your most important piece. In games like the king's indian defense, e5 is played but black almost always wants to go for the f5 break to trade pawns with e4 and then the bishop gets freed. So let's talk about your game 6 move 7. 

In this position, you're annotation is 'Not sure if e5 is better. I was preparing for d6 actually'. That is a very weird annotation, given what I've already written. According to the chess.com database, there are some master games in this position. None of them play e5 here. And a lot of other moves have been tried: Nf6 (the knight block is only temporary), Qb6, d6 (I also don't see why you didn't play this immediatly if you wanted to play it), Qc7, h5, e6 and Rb8.

Further down the game there's this:

And you're annotation is 'somewhat of a weird take'. Again seems to be a very justified take. Now white played very good moves here. He could have also taken on d7 instead of g7, too. Even if white didn't have these tactics, I feel the rook trade for the bishop is justified. In your game your kingside has a hole and white has a black squared bishop to penetrate. I would much prefer white here, trying to take advantage of this.

@SpelerThomas I might have written the annotations from white's board perspective. As mentioned I'm new to Sicilian (basically testing and wondering if I should try to adopt it as main defense against E5). I also didn't know DSB is considered so strong. Actually I don't know how I feel about Bishops at g6/b6 versus solid 3 pawn structure in front of my king. I have had mixed results with Fianchetto'ed bishops. 

Hyper accelerated dragon is an excellent opening to master that will take you well beyond 1400 when you get really good at it. Keep practicing it! 

Game #9: White, 15|10, win:

With this game I crossed 1200 in Rapid. I played a d4 opening. Starting to study these as I like the positional nature of them. As with other openings I consider myself a beginner in the area, so comments (learning materials) regarding main/side lines are welcome. The game went more or less the way I wanted to. He made a blunder that decided the game really quickly, but there were a couple of positional decisions to make. I also ran an engine analysis on this game. However my comments are not affected by it.

Here Bb2 is a weird move and the bishop looked at its own pawn the rest of the game. If you intend to play Bb2, then you should already think about how you're going to solve the issue with the pawn on d4. There are some ideas, but you have to really think about those kind of things. Also your opponent has a bishop on g7, so if the board opens up be aware that if you are the one to open it, your bishop may be unprotected. In my opinion your bishop would've been much better at d2.  

Yes, Bb2 doesn't make much sense. 

gg

Move 19 ( Nxc7) was pretty risky, your opponent just had to play one of the rooks to c8, and then you're down a knight, because there's no safe move for your knight to go. At move 19, I would have captured the opponents bishop on the g7 square, you were already ahead a piece, so why not take out the guard? On the brightside, you are showing gradual improvement, and congratulations on getting to the 1200 mark.