As the title, is there a crossplay between ps5 and xbox x? And how do you invite friends from other platform?

There is no cross-platform but there is cross-generation play. .....e.g. PS5 to PS4.

You can create a group on the main screen. In the upper right hand corner it will have your avatar and if your press triangle (on PS), and click the plus icon, you will be shown your list of friends. You can then send invites that way. Their avatars will be added up top next to yours and then when you join a game, they will come with you.

The group leader will have a crown shown in their avatar. ....the one who everyone joins on and who will select the game(s) the group plays.