does anyone know how to delete alot of contacts at once because i accidently got 3000 of my dads contacts and i only need about 100 of them

You can sync them to an app on your computer, as described in the manual, then bulk delete them there. You can do the same with iCloud.

If you don't want to do either of these (and you really should do at least one of them to protect against loss of your contacts when the iPhone iOS crashes and wipes out your data) then you need a 3rd party app like Speed Names. It sort of allows bulk delete by tapping each of the contacts you want to remove, then tapping the "Delete" button.

I would login to icloud.com

Click your contacts

Multi select your contact with Shfit down and click the cog at the bottom and delete,

I think that may do you, assuming of course you use the cloud!

How, exactly, did you get them to begin with? If your phone is syncing to his iCloud account, when you delete them, they will also be deleted from HIS phone...