First, use DiskWave to see what is "eating up" your disk space.
Download DiskWave from here:
DiskWave Homepage
It's small in size and free.
Open DiskWave and go to the preferences.
Put a checkmark in "show invisible files".
Close preferences.
The DiskWave window shows you all your volumes and drives in plain English (no ridiculous graphical formats).
Click on any item "on the left".
Now, you'll see what's ON the volume, listed in order of "largest to smallest".
You can easily locate what's eating up your space.
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You can also try the free "Monolingual" app to remove non-English language resources. Version 1.8.2 still seems to work with Monterey to remove language resources from 3rd party apps.
Monolingual
ingmarstein.github.io
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Finally, keeping enough free space is really a job that's "up to you".
In other words, you can't "use apps to do the thinking for you".
YOU have to look around, and decide what really needs to be there, and what can be thrown out.
If you have large libraries of music, pictures, and [especially] movies -- that seem to be "growing" -- realize that these can be moved to an external drive, and will run just as well from an external drive as they do from the internal.
I'd look for an external USB3 SSD to hold them.
But also remember:
If you move files to an external drive, you also have a second drive TO BE BACKED UP. Important files are never "safe" unless they exist on two (or more) drives at once.