How to get free gb

You cannot increase the storage on your phone as it is a physical part of your phone. The iPhone 7 is fairly old, and you could benefit from upgrading to a newer model with more storage. If you cannot upgrade to a newer model, you can try offloading photos and videos as well as other data to iCloud, but doing so will most likely require the purchase of an iCloud data plan.

First. Reboot your iPhone, it will most often reduce the "Other" Storage.

Then, go to:

Settings -> General -> iPhone Storage

Look for which apps take up space.

If you have many Photos, go to:

Settings -> Photos. Check in Optimized iPhone Storage.

This will save a smaller copy of your photos, and save the original in iCloud. It requires that you also enable iCloud Photo.

Remember that you need to have enough storage space in iCloud. You have 5GB for free.

You can read more about how to upgrade iCloud Storage here:

https://support.apple.com/en-us/HT201318