IOS system data takes 65% of my iPhone 128GB

Keeping in mind that the “other" or "system data” storage category is mostly filled with cache and system files created by Safari, the Mail app, other apps and iOS/iPadOS itself, that space is automatically managed by the operating system and you can’t interact with it.

That said, if your device is running iOS/iPadOS 13.6.1 or later, see this support article: Clear Other storage on your iPhone or iPad - Apple Support

If you already tried (to no avail) those steps, some benefits to reduce that space can be also obtained creating a full backup of your device, then restoring it to factory settings and, in the end, setting it up as new, as per these instructions: Restore your iPhone, iPad, or iPod to factory settings – Apple Support

When done, restore data from your previously made backup, then restart your device and check your device storage again.

If the issue persists, contact Apple Support directly, using this link: Get Support

Regards

Giulio

DJCachuera wrote:

I restored from Mac Book backup, but now it’s worst!

Better. That’s your data, cached locally for quicker access. You would rather waste that storage, and wait for downloads?