When I bet for some voodoo card, and someone bets my bid, the credits do not return to my wallet. and when I'm bidding again, and again, it goes exausted fast. I don't know, after the auction is complete, do all my unused credits return to my wallet? or do they vanish?

When you are outbid, the credits return immediately to your account.
If you experienced something different, click on the Contact Us link at the bottom of the page, write the problem and we will look it up.

Generally, we have never had an issue like this so just check again. You can check your remaining credits by clicking on the turns count.


PS. Welcome to the forums