I don’t have enough space in my iPhone

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)       

If you have an iPhone 6 as your profile shows, it can't be update to IOS 13. See the Apple Support article(s) below.

iOS 13 and iPadOS are compatible with these devices - Apple Support.    

Update your iOS device.        

Get help with over-the-air iOS updates          

Update – Can’t or can’t restore 

Have you tried using iTunes on a computer or Finder if running Catalina to do the update?

 Update software on iOS devices in iTunes on Mac

If you see an error when you update or restore your iPhone, iPad, or iPod      

See the information in About storage on your device and in iCloud - Apple Support