I'm having trouble "allocating" some free space on the "file partition" to the volume that contains the system files: an encrypted APFS container. I would like to do this because I am no longer able to update a large app from the App Store. I have already read a few articles dealing with the problem of resizing APFS containers but they still don't answer my question (or maybe I didn't clearly understand the idea). I use a MacbookAir under Catalina.
I have put some screenshots which can give more useful information.
Reduce this volume to 90 GB
Increase container capacity to 160 GB
Thanks for your help.