How do I free up storage space on a MacBook Pro with macOS Big Sur?

Memory problem.

I'm not using my computer that much ad not saving basically anything on the HD, but I'm receiving messages that is almost full at its capacity (now I only have 100 MB from a 256 GB capacity). I have cleaned the cache from time to time, but the problem persists, any recommendations? MacBook Pro 2014 15 inches running on BigSur.

[Re-Titled by Moderator]

Original Title: Memory problem