I will start my activity in the forum here by creating my on study journal.
My goal is to play at least one real time game a day (plus many simultaneous games on DGS) and doing tsumego for at least 10 minutes a day.
Also I try to review each of my own games when finished and post some interesting or problematic ones here.
I think some help of you guys would really bring me further, so any comments or reviews are very appreciated.
Of course I will also try to review the games of the weaker players here as well (as a side effect it also helps me improving
)Btw, I always write some notes into the sgf files to explain some main issues where I could need some advice.
Thanks in advance and I hope you will enjoy my games and be part of my learning process
: My first thought is to play R13. I think you're right to play on the right, but with your move, white potentially has the advantage top right.
I'm tempted to R12 and "see where white is going with this". My reasoning is that R12 is a good move and white also wants/needs to play there.
white's weak groups have connected and become strong, and now black needs to worry about the UR corner group and the thin right side. What happens if white dives into the 3-3 point?
is quite the big point for the moyos.
, your A B C seems better. It may be worth considering just playing C directly, as you don't know if you'd want A or 
maybe consider F15, as black owed a move in the corner to prevent white from living there anyways, and this prevents the connection under. Whatever happens, don't let white run through the middle of black's moyo unless you are absolutely certain you will kill, or otherwise need to bet the game on it. Much better to give up a bit to turn the rest into territory, especially as white has the connection under in the game. The sequence around move 56 or so is painful, as black went from having a moyo to driving white right through it and creating a weak group from what used to be thickness. 
begs white to fix his shape up for free.
What is the purpose of this stone? If you want to use the aji, better to play K3, since it breaks the ladder AND is a move black wanted to play anyways.
. 
feels like a casual remark but it's exactly these tiny details, which are game-deciding in the end. I have to learn that the hard way in many of my games, too 
Endgame: at J18 is middlegame. 
From the wrong side. 
The position is quite distressing for Black now. You really need to play D11 and hope the central group doesn't die.
I think white just removed the chance of him being able to invade at H3, and his next move is pretty small so I like the tenuki.
I think kicking here is an option because white can only get a two space extension from his two stone wall, but I hate the aji in the corner after the kick so I would probably just play your move.
and :b139: you have the right instinct but you do so too thinly. When surrounding the opponent or defending a territorial border, pause for a few seconds to see if your lines can't be broken too easily. Otherwise you must be a little more patient and wait for an opportunity to surround without defects.
. Here it must be correct simply to extend along the top side. Try L17. This makes some territory easily.