Hello Oleksii_iOS,
Thanks for posting in Apple Support Communities!
We understand that when checking the internal storage on your device, Documents & Data is taking up space but you select it, you’re seeing “No items.” We’d to help.
Do you have any items in Files? Documents & Data such as document files are stored in Files. Here’s how to Use the Files app on your iPhone, iPad, or iPod touch.
Try to restart your device, when you check internal iPhone storage are you seeing the same “No items” message?
We would also suggest updating the iOS on your device. Make sure to back up before you Update your iPhone, iPad, or iPod touch.
Have a nice day.