I brought space and my storage keeps saying it’s full?

As the article you got here from states… You rented storage to offload contents, and not an upgrade to internal storage. There is no internal storage upgrade. What an iPhone ships with is what it will have. And apps can and will need local storage for various tasks.

That article again: What's the difference between device storage and iCloud storage? - Apple Support

Some ways to offload contents: How to check the storage on your iPhone, iPad, and iPod touch - Apple Support

An iPhone under-configured for your current and likely future storage and app usage will never not need to have its storage managed, unfortunately.

See if anything here helps. 

Disk space - How to check the storage on your iPhone, iPad, and iPod touch.    *

 Disk Space – Free Up    -

 Disk Space – Free Up (2).  -

 Disk Space – Free Up (3).  -

 Disk Space - Free Up (4)    -    

 Disk Space - Free Up (5)   -  

https://www.youtube.com/watch?v=bnhuHSv_WrI