Update software

Please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support

If the above Apple articles do not help, please post back with relevant information. 

Sorry, but the answer is clearly shown in your screenshot. Until you follow the instructions to create more space on your device, it can not be updated. This is not something the other users here can accomplish for you.

Not possible. You need an iPhone 6s or newer to run anything higher than ios 12.

What happens when you attempt to update?

Any error messages?

Which device?

What is the existing version of iOS?

What happens when you attempt to update?

Any error messages?

What is the existing version of iOS?

Try actually reading the information in that screenshot.

Can we assume you have already solved your tech support issue by merely posting the text above? If so, well done, otherwise please answer the other questions.

Please see:

As to why you could not provide this information in your initial post, I really don’t understand.