How yo get more GB

You can't increase the storage size on your phone, it is a fixed size.

Freeing up storage space on your iPhone.

Here are some helpful articles that can guide you on how to free up storage space on your phone.

How to check the storage on your iPhone, iPad, and iPod touch

https://support.apple.com/en-us/HT201656

Manage your photo and video storage

https://support.apple.com/en-us/HT205703

Clear Other storage on your iPhone or iPad

https://support.apple.com/en-us/HT211686

You can not increase the amount of storage on any iPhone