Safely delete old "Macintosh HD - Data" partition?
Firstly, your Macintosh HD and the snapshot following it are mostly linked to the same blocks in the APFS container. Their total size on disk is lot less than 44.2 GB.
You MUST NOT try and remove Macintosh HD - Data. That is where all your apps, settings and data are stored.
You have a very small internal disk and will always be constrained as to what you can store on it. My best advice is to:
- Make sure you have a good backup (using, for example, Time Machine) in case of problems.
- Buy and connect an external SSD (e.g. a Samsung T7). Format it as AFPS.
- Move some of your files (documents, photos, etc.) to the external SSD. Depending on your version of macOS and apps you use, you will need to take care moving stuff. You will need to keep the external SSD connected at all times.
- Make sure you are backing up the new SSD.
As an alternative, you could take advantage of macOS's "Optimise Mac Storage" feature that allows you to transparently store most of your documents (and other files) in iCloud. This will require an iCloud subscription and permanent Internet connection. I very much prefer the external SSD solution.