I have two questions about my latest game:

1. Is my move No. 19 correct or is there a sharper version? Because this move is not bad but as you'll see in the sequence I lose sente without gaining anything, but just stopping white extendability.

2. Is my move 31 the best possible? I always feel odd playing moves that leave my a one-dimensional moyo....

I think that is fine. You might tenuki with , however. After you have prevented a White extension with sente.

After a White extension on the top side is bigger. Therefore a Black extension there is bigger, too. Also, after Black settles the bottom right corner the right side is not so big. Both factors point to a Black extension on the top side.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Thx, Bill. The idea with tenuki in move 23 is kind of cool.

I have trouble understanding tenuki with move 23. Move 24 white then cuts and gets into center, making previous black moves look meaningless.

This is similar to the joseki where White makes a one space high approach to Black's 3-4 point stone, then Black attaches underneath, White hanes on the outside, and Black pulls back. Now White can, and often should, tenuki, leaving the cut behind. In that joseki a solid connection by White is sente against the corner. Here the connection is gote.

The idea of preventing, with sente, your opponent from doing something is important, but the only place in the go literature that I have seen it explicitly taught is by Takagawa. Yet it marks the beginning of modern fuseki thought, a few centuries ago. At that time games often began with Black playing on a 3-4 point, White making an approach, Black playing a pincer, and then White tenukiing. White could be satisfied with preventing a Black enclosure with sente.

In this case Black may regard and as kikashi, and treat them lightly. If White cuts, Black has the option of extending on the third line to threaten a ladder, and when White prevents the ladder, Black can make a base. Or Black can tenuki again.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Here is a new game from me, playing with black. It's one of those where u don't know exactly where u lost it so advices are very much appreciated. IMO my move 67 is very slow and I should have played tengen instead, agreed?

I think your 67 looks fine. It strengthens and extends your moyo while threatening to cut H15.
Move 50 of white was a mistake which you could have simply profited from by just defending against his threat. You instead decided to fight, which feels a little like you want to help white make something out of his E13. Also you fight in an area where is not much to take.
The reason it feels especially weak is that black is weak on both sides of this fight. As white you don't even want to kill an invasion on top but use it to influence the center, minimize the black influence on the right side and increase the value of invasions on the open left side.

I see that very often in your games. I.e. move 5 of this game. You play like the top left corner is yours. All the following moves show that, too. Also look at move 21. After move 42 white has a big corner (much more than it should have expected on the bottom side with all these low stones). And the right side moyo of black is deeply wounded. All that is the result of that pincer. Also the 3-3 invasion at move 60 is desperately trying to help white, while D12 is still open for taking some profit, since many moves.

If you look for pointless moves you can try K14 (move 76). But everybody does that from time to time. I think you can't learn much from these. But u can learn from these mistakes that form a pattern. My guess is that u often worry that u play too slow and that this is the reason of u losing a game. So probably that fear leads u to overestimate the power of ur attacks, which then actually help ur opponent. Maybe instead of finding the points where u played too slow, u should look out for slow moves that don't bring u into trouble and actually are cash machines, like the stretch of 67 or D12 which u played way, way, way too late.

Last but not least I want to add that I'm around 4k at the moment, so I might be totally wrong. Anyway I hope it might help u grow stronger!