Without knowing your definition of "usual things" it's hard to know what you've really checked.
First thing to check is Settings > General > iPhone Storage. That will show you what apps are the top users of storage space on the device, and also will often suggest changes you can make to reduce storage usage. Check the setting for each app that's a major user of storage - some apps, including Messages, Music, TV, and Podcasts give you options to review/delete individual downloads.
Here's a list of features that will help automatically manage on-device storage use (based on iOS/iPadOS 14):
iCloud Photos > Optimize Storage
iCloud Messages - if iCloud Messages is enabled (Settings > [name] > iCloud) then it automatically uses a feature similar to iCloud Photos' Optimize Storage - it will reduce on-device storage once the messages have been synced to iCloud
Music app - Also has an Optimize Storage feature - Settings > Music > Optimize Storage - helps manage downloaded music (media downloaded from Apple - iTunes, Podcasts, TV, etc. - is never copied to iCloud storage - if deleted from the device it's re-downloaded from Apple)
It's worthwhile to compare the amount of storage space being used in iCloud for iCloud Photos and iCloud Messages to the on-device storage for those functions. If the amounts on-device are equal to or greater than the storage being used in iCloud, then there's a problem somewhere - those features may not be syncing correctly with iCloud.
When iCloud Photos > Optimize Storage and iCloud Messages are syncing as they should, you should see results comparable to mine (64 GB iPhone X, 54 GB of 64 GB Used):
iCloud Photos storage: 100 GB
Photos on-device storage: 3.5 GB
iCloud Messages storage: 7 GB
Messages on-device storage: 1.2 GB