Hello

In our game we want to use sounds based on  https://gamesounds.xyz/. I mean that sounds in game would be mix of  those from GameSounds and our own recordings. For example sound of explosion would be mix of burning effect from GameSounds and 'boom' made by our sound designer. I know that all sounds on this sites are free for use commercially, but what about licences? It would be enough that in credits would be mention that some part of sfx were made with those from GameSounds.xyz ? Is there another for of reference needed?

Regards
Crane

A licence is just the right to use the track, and the terms under which it is used. That website doesn't specify the licence clearly so it's not possible to give you a definitive answer on what you have to do in order to comply.

Actually as stated on the site, each library (.zip file) comes with a LICENSE file inside it stating the licensing requirements for that particular library.  You'll have to read over these files for each library you want to use (as they can be different, between libraries) from the site.

In general, you need to be very wary of any sounds (or any other kind of creative files such are art, etc.) you download from the internet. It is very common for sites to take material that they don't own and post it "free to use."
For example, I see "BBC Sound Effects library" listed on that site, with files posted from a couple years ago.
The listing looks suspiciously like the "BBC Sound Effects Library" which Sound Ideas currently sells for $395

https://www.sound-ideas.com/Product/152/BBC-Sound-Effects-Library-Original-Series

(note; The BBC just a released a lot of sound effects literally 2 days ago, but they are not for commercial use).