Why the card can not be saved in the needed desk for a long time because it has the loading icon?

[Іван Григорійчук]

It is not because of bad network connection)

Can this be the result of fullness of my desk(free limit…)?

[Rishabh S]

Hi @Іван Григорійчук , :)
Hope you are doing well,
Welcome to the community!!

I took a look at your boards and noticed that one of them has around 5000 cards. 
In Trello, whether you're using the free or paid version, there's a limit of 5000 open cards per board, which is explained here: https://trello.com/1/resource/limits. 

To keep adding cards, you might consider creating a new board or moving some cards to another board.

Thanks.