Can i upgrade my storage, how?

you cannot expand the capacity of your iPhone.

you may be able to utilize iCloud storage to help free up space..

otherwise you may simply have to delete stuff to free up space.

What's the difference between device storage and iCloud storage? - Apple Support

The storage space in an iPhone is a fixed size and can't be increased.

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