Other storage taking up too much space

There are various things that constitute 'Other' on an iPhone.

In Settings, open iPhone Storage. Scroll down the bottom of all your storage. It will show System and Other.

On my iPhone, System and other are taking up 6.7Gb, which is only 0.8 Gb below yours.

If you can, create space by offloading apps that you don't use, or only use occasionally. You will be given the choice of Offload or delete. Offload gives you the opportunity to reinstate it at a later date without losing any data stored within it.

Back up your phone then restore it from the back up.

If you go into your voice over settings and delete the voices you don't use, that free's up LOTS of space. It freed up 10GB for me. Just swipe left on the voices you don't want and it will delete.

If you delete the voice over voices that you don't use it will get rid of lot's of them, it helped a lot for me.

I have 30gb of space being used by 'other' - it's only just appeared since I connected my phone to my mac yesterday (I don't normally connect it). I've off loaded apps as suggested hardly any difference made. I had over 30gb of space 3 days ago.

I did do some 4k videos, which I have since deleted. What's going on?

Whenever I try to clear storage, it will always bring back the storage and I only have 2 apps!

No, Apps has a place all of its own. You'll see it as Apps(Settings>iPhone Storage) in the horizontal bar: System, Media Apps Other.

Other can be all manner of stuff like mail, but not the Mail app,, cache, history, trash.