This is a bit naive maybe, but on the other hands it may help new users with older smartphones with little memory.
I was wondering why the memory on an Oneplus X with only 16GB was always full. I couldnt delete anymore files in the settings. Then I found out, that in settings → About the phone → System Updates all the old updates are saved. You can delete them right there and voila: there is much more space left in your memory now!
Regain your privacy! Adopt /e/ the unGoogled mobile OS and online services