Need more GB to my iPhone 7

you can buy more iCloud storage...

Buy more iCloud storage - Apple Support

Just make sure that you understand that this is NOT expanding the capacity of your phone. You need to take additional action in order for your iCloud storage to save storage space on your phone.

About storage on your device and in iCloud - Apple Support

You can’t. Storage on an iPhone cannot be expanded.

You can't add to the storage capacity of any iPhone.

You would need to buy a new iPhone. Internal iPhone Storage can't be expanded, sorry.

You have several responses to your question already.. Have you read thru them?