Hi! I'm going to give access to my dev friend to my itch.io project where i uploaded a game, but i'm scared he will make sone mistakes or even grief the page, so i'm asking if i can save the page (like making a backup) so if he greef it i can reupload the page before he destroyed it, Thanks!

There’s no way to “back up” an entire page and its design unfortunately. You would have to manually copy and paste the parts you want to save. You can download the files you have uploaded if you wish to store a backup of them.