How to reduce the size of Other data
You can’t get rid of Other entirely, but you can sometimes reduce its size. For example you need a space for free pdf scanner app.
Let's try clearing the cache in Safari first. Go to Settings > Safari and select Clear history and website data. If you have a lot of Safari tabs open on your iPhone, you should also close most of them. You can also edit the Messages section to keep fewer old messages. Go to Settings, then Messages, and scroll down to Message History. By default, messages remain fixed, but you can change it to a year or even 30 days to reduce the amount of data messages stored.
Finally, go back to stock iPhone mode and check the list of apps. Most applications store data classified as applications, but some caches are classified as other applications. For example, if a podcast program takes up several gigabytes, most of it is probably stored in the cache. Uninstalling and re-downloading the app may create a cache in the "Other" category.
The Basics: Using iTunes to Backup, Restore, and Restore. This may take some time.
The best way is to use iTunes on a Mac or PC.
Connect iPhone to computer and launch iTunes. On a Mac with macOS Catalina or later, you use the Finder, but the process is the same. You may be asked for permission to use your iPhone and asked to enter a passcode, which you should do.
Select your iPhone by clicking the small phone icon in the upper left corner, then select this computer under Backup. It's worth secretly checking your local backup to ensure your account passwords and health data are also backed up. All you have to do is choose a password that you will never forget. Click the Book Now button.
When the backup is complete, disconnect the iPhone and go to Settings> General> Reset and select Erase All Content and Settings. This will restore your iPhone to normal. After it restarts and resets, reconnect it to your computer with iTunes open and follow the on-screen instructions to reset your device.
This is the longest and most demanding way to reduce secondary storage, but it is also the best; Unable to update after reset and reboot.