Good afternoon Jonas00,
Welcome to the Apple Support Communities!
It sounds like you are having issues with verifying your account, and we'd like to help.
The resources below will provide some guidance:
Manage two-factor authentication for your Apple ID from iPhone - iPhone User Guide
"On a trusted iPhone, iPad, or iPod touch, go to Settings > [your name] > Password & Security, then tap Get Verification Code.
You won’t be asked for a verification code again unless you sign out completely, erase your device, sign in to your Apple ID account page in a web browser, or need to change your Apple ID password for security reasons.
Add or remove a trusted phone number
When you enrolled in two-factor authentication, you had to verify one trusted phone number. You should also consider adding other phone numbers you can access, such as a home phone, or a number used by a family member or close friend.
- Go to Settings > [your name] > Password & Security.
- Tap Edit (above the list of trusted phone numbers), then do one of the following:
- Add a number: Tap Add a Trusted Phone Number.
- Remove a number: Tap next to the phone number.
Trusted phone numbers don’t automatically receive verification codes. If you can’t access any trusted devices when setting up a new device for two-factor authentication, tap “Didn’t get a verification code?” on the new device, then choose one of your trusted phone numbers to receive the verification code."
If the issue persists, you may need to reach out to Apple for help with this:
Contact Apple for support and service
Take care.