What is taking space in my iphone

Check this link...

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

And this link...

Clear Other storage on your iPhone or iPad - Apple Support

Follow this

Clear Other storage on your iPhone or iPad

If you have iOS or iPadOS 13, your iPhone or iPad storage is full, and the storage is mostly taken up by "Other" storage, update your device to the latest version of iOS or iPadOS.

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