Looking for compositions database

Hello,

Some book authors suggest to solve chess compositions to improve own calculation and visualization abilities. I have looked in internet for a database with not complex/intemediate level compositions with comments and solutions but have not found nothing. Does anybody want to share a database of this with me or point me to where I can download it?

thanks

Here's a couple of suggestions:

Do a search on chess engine test suites (or something similar).

A test suite is a collection/database of positions, (not games) with the best move given.  Ideally, your chess engine (or just you, in your case) should be able to determine and confirm the best move in each position.

One such website, with a whole bunch of test suites, is here.

You will, or course, need a GUI (Scid vs. PC, Arena, WinBoard, Tarrasch, Fritz, etc.) to be able to load each position.

Another suggestion is to just solve tactical puzzles by visiting sites like Chess Tempo.  These types of puzzles will definitely help to improve your calculation skills.

Just look for studies (study) on chess.com - there are plenty of them.

Chess compositions can be found on yacpdb.org . There are plenty of them...