Hi theresa_nasr1
welcome to the Apple (user-to-user) Community.
Re : "i want to update my software"
Seems there are very few Gb free for your iPhone's iOS to use, in order to do what you ask it to, so iPhone isn't up to doing much or intensive or memory work. (Many people would keep around 8 Gb free at all times, for smooth operation of the iOS.)
To see what all the storage space is being used for:
How to check the storage on your iPhone, iPad, and iPod touch - Apple Support
To manage the storage space, if you wish:
What to do: If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support
All the best :-)