So i just created my own server and it lets me in fine even before i made myself an admin and it wont let my friend join its saying mod mismatch? Could it be one of my mods or is it his problem or ? need an answer thanks

Generally when you see a mod mismatch error just restart the server and your steam as well. If your server has a green 'Up to Date' notification, then chances are the mod mismatch is because the player's computer hasn't gotten the update. In some cases this is due to auto updates being turned off. In this case ask players to delete the mod folder (ex. 35834391 in Content > Mods of the Shootergame folder, then subscribe again to ensure the files were properly downloaded.

Okay thanks that helped us there but the next issue is that my server is constantly crashing after about 5minutes of it being up i also tried completely deleting the server making a new one and i also wiped it multiple times and have done hundreds of reboots

Most probably that's an Ark or some mod issue. Disable all the mods and see if that helps.