How do i tell if someone is hack in my phone

Run safety check to make sure no one else is logged into your account and that you are not sharing any information. It would not be your iPhone that is hacked, it would most likely be an account that has been compromised by someone knowing your Passcode/Password. You will also have the option to change those here as well.

How Safety Check on iPhone works to keep you safe - Apple Support

What makes you think that you've gotten hacked? iPhones are really difficult to hack, unless you have jailbroken it or you've shared your Apple ID password there is nothing to worry about

If you feel unsafe you can always change your Apple ID password

When I first noticed my iPhone having issues with being hacked I put my phone into lockdown mode. I know most people believe iPhones are difficult to hack and yes at one time they were. Until apple decided to start sharing the same processing unit as windows. Now they're just like any other phone. Mu suggestion is to activate lockdown mode and leave it there no matter what. If someone is really determined to continue messing with you after that, they'll start blocking your signal. Best of luck to you! It worked for me until I stupidly turned it off for 5 minutes to do something then it was done for. Also, one lady thing. Keep in mind that you may very well have to change phone numbers, service provider and possibly even sim card. I had to. It worked until I was stupid once. Best wishes!