The following are common ways to clean up memory:

1. Clean browser history and website data:

Go to phone settings > Safari browser > clear history and data.

2. Clear the expired SMS content:

Go to settings > messages > keep messages > 30 days.

3. Delete unnecessary applications:

From "Settings > General > Iphone Storage Space", find an application that occupies a large storage space, and click "Delete Application".

4. Close some uncommon applications:

Go to Settings > General > Iphone Storage and click the Enable button to the right of Uninstall Unused Applications.

5. Delete the file retention of photos and videos:

Open photos > recently deleted > select > delete all.

Personal suggestion: If the memory is still insufficient after cleaning, you can try to clean it with a computer or find a professional to clean it.