HOW TO EXPAND GMAIL STORAGE

Firstly you can go to Storage Space to view and analyze how much storage have you used till now:

Go to the Drive storage page and select “View details.”

then you can find it is gmail,google photo or something else that uses the space.

secondly, if you identify that you can not delete and drop the stuffs you find in your google storage, you can buy storage from google in order to expand your gmail storage