I tried to install ios 11 few days ago and it said an error occurred installing ios 11. I have iphone 5s. Why is this?

I deleted many photos and it says again that i have 0KB storage, i can't delete other things because i need them. And when i press install it doesn't say you don't have enough storage, appears verifying update and after 30-40 secs it says an error occurred installing ios 11. Why is this? What do i do?

You plug into your laptop and let iTunes do the install.

Hi