I ‘ve purchase 50GB for storage so it added to my iPhone storage ?

No. See What's the difference between device storage and iCloud storage? - Apple Support

Your iPhone remains with the same amount of storage it was purchased with.

You can free up some space by activating iCloud Photos and optimizing iPhone storage, for exemple. See Manage your photo and video storage - Apple Support

This might also help a bit If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

50 GB of iCloud storage doesn't add storage space on your iPhone.

What's the difference between device storage and iCloud storage?    *

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