Hello sequana33,
Thanks for that info and for choosing the Apple Support Communities. If we understand correctly, you are having an issue with storage on your iPhone. If you haven't already, please restart your iPhone as iOS clears cached data and does other system optimizations when you turn your device off and on. Then check your storage again:
Restart your iPhone
What's the difference between device storage and iCloud storage?
Make sure your iPhone is up to date, as the updates contain stability fixes that can resolve issues like yours, as well as important security updates to keep your iPhone safe.
Update the iOS software on your iPhone, iPad, or iPod touch
Cheers!