Hello guys, can you recommend any ways to improve calculation

depends on what type of calculation. if you want tactical vision, I would recommend the scotch game. it has plenty of good opportunities for traps and sharp plays to spot depending on how you play it, and it works well for beginners and even masters

"... Most internet players think that 30 5 [(30 minutes with a five second increment added every move)] is slow, but that is unlikely slow enough to play 'real' chess. ... Many internet players are reluctant to play slower than 30 5 so you might have to settle for that as a 'slow' game." - NM Dan Heisman (2002)
https://web.archive.org/web/20140627010008/http://www.chesscafe.com/text/heisman12.pdf
That was back in 2002. These days, you might have to settle for 15+10.
"... There are several problems which can arise as a result of Kotov's method. ..." - Secrets of Practical Chess by GM John Nunn
"One of the pioneering works on the art of calculating, THE INNER GAME OF CHESS by Andy Soltis appeared to excellent reviews in 1994. Now an updated and expanded edition of the original has been published by Mongoose Press. ..." - IM John Donaldson (2014)
https://web.archive.org/web/20220625174132/https://www.jeremysilman.com/book-review/inner-game-of-chess-the/

I'm probably the last person who should comment about calculating moves. I have trouble calculating moves even though I play nothing but correspondence chess. But I'm going to make some comments anyway.

Two things come to mind about calculating moves into the future. I read about both of them from a couple of chess books I have.

1. It's not enough to be able to calculate moves, you must also be able to evaluate the resulting positions as well. Now as I have already said, I cannot calculate to begin with, but I did read this somewhere. Perhaps it was in the book, 'Chess Tactics from Scratch' by Martin Weteschnik.

2. Most of the time, it's enough to calculate two and a half moves ahead. That's three moves for you, and two for your opponent. I read about that in the book, 'Studying Chess Made Easy' by Andrew Soltis.

So there you have it , and from somebody who cannot calculate to save his life.

No applause please, just throw money.

@tpr said ^

Think Like a Grandmaster by Kotov teaches how to calculate efficiently.
Here he calculated the queen sacrifice 30...Qxh3+ 20 moves deep.
https://www.chessgames.com/perl/chessgame?gid=1084375

If there is something to be learned from watching modern top grandmasters live, in the Sinquefield Cup for example, it is that: There are no 20 move calculations. It is only afterwards in the analysis that such monstrosities come to life.
Your own source says:
"Don't worry about it. Kotov sacced his Queen on spec and did not find the win OTB.

From moves 33 to 40 Kotov repeats the position taking a pawn on move 38 to avoid a three fold rep. The game was adjourned at move 40 and Kotov worked out the win from his hotel room."