How to improve at sharp positions

I have noticed in my games (especially faster time controls) that whenever I get a tactical or sharp position I tend to blunder or think too long which leads to time pressure causing me to lose the game whereas in games with calmer, less tactical positions I am able to play fast oftentimes with accuracy >90
What could be the reason for this? I don't think my tactics are particularly weak as I can solve difficult puzzles if I actually try to.
How do I improve my chess in tactical/sharp positions? Please feel free to look at my games and give me your opinion.

I would suggest studying the games of a great master of the past who was really good at stirring up complications. Specifically, Alekhin and Keres come to mind.
Botvinnik wrote this of Alekhin: "he had a masterly way of finding the way to complications at the right moment"

Play more tactical games

Usually this kine of problem is not a question of solving exercises or studying grandmaster games.

My advice is:

1 Play slower time controls: rapid instead of blitz or blitz instead of bullet.
2 Play with increment.
3 Study your games (with an engine). Look at the moves that lose 3 or more pawn units. Look at alternative lines given by the engine.
4 Find a pattern in those moves. Do you overlook tactics available to you? Do you overlook tactics available to your opponent? etc.
5 Ask yourself whether you considered the move you should have played during the game or not. In sharp positions there often are several possibilities; ideally you should see all of them and choose the best one.

1 and 2 should enable you to play reasonable chess (look for good moves and still not to lose on time), which is needed for improving.
3 to 5 should help you form a picture of your strength and weaknesses. Then work on those.

I found out that I tend to underestimate my opponents tactical options while I am pretty much aware of my own. So I try to be extra careful once I started an attack.

simple..
Train to enhance your evaluating technique..

This hardly seems amazing. Sharp positions are more complicated.

I only own 1 book,Bobby Fischer my 60 memorable games

If we/you struggle at proper calculations at rapid or classical one usually doesn't calculate better with less time to do so.

Play 50 training games at 20min.
Force yourself to check minimum 3 options 4 moves deep on less than obvious moves. Even so, even if move seems obvious practice looking at a couple alternatives. More complex positions look at 4 options starting with 1 piece. Nope? Next piece. Nope? Next piece? Maybe... Next piece? Oh they will either loose their queen or rook or after trades I'm up +3 and now they can't castle.

Bullet and blitz just trains people to be lazy with calculation. If just for fun then I guess calculate faster. Which won't happen without practice but whatever. If wanting to seriously compete in tournaments then get good at calculating in classical first.

@dokoko1 said in #4:

Do you overlook tactics available to your opponent?

To OP:
I think this is the most usual happening, for example in the game vs. dragowebs, your move 25.dxe5 ignores the various threats posed by the Black pieces. Obviously you were time pressed and somehow previously reached a position with little coordination between your pieces, just the opposite of Black. Maybe you are launching attacks a little too early, without the right preparation.