Hey @KOSTA, welcome to the Glitch Forums!
As @MewKirby points out Glitch does have built-in support for custom domains but as you may have noted they require you to have soent some time helping other community members.
You can also add a custom domain manually as the links above indicate. Those are a little out of date, though; a better place to look is [Tutorial] custom Domain with Glitch or [Tutorial] Get your Glitch project on a domain!.
Hope this helps!