I messenger no longer on iMac

Hey there GusatAAAP,

Upon researching your question, we were able to find the steps to save or delete conversations in Messages on your Mac: Save or delete text conversations in Messages on Mac As you can see, there's not a way to recover intentionally deleted messages.

If you didn't recently delete those messages, we want to learn more about what's happening, along with ruling out some possible causes:

1. Did this occur with all of your iMessages on your Mac, or only some of them?
2. When did this start to occur?
3. We see you also use an iPhone, but are the iMessages(blue texts) still on there?
4. Sometimes unexpected behavior can be resolved with a restart. Check out the section ‘Restart your Mac' here: Shut down or restart your Mac
5. From your post, we see you have macOS 10.15 installed, but the latest version is macOS 10.15.7. You can verify this by clicking on the Apple logo at the top left corner of the screen, then on ‘About This Mac’. In case you needed it, this link shows how to first back up, then Update macOS on Mac.

Cheers!