Unable to manage system data files in macOS Sonoma 14.6.1

System data files have filled 80% of my Hard Drive and there is no information on how to manage these in Sonoma 14.6.1 There is not manage button, no system optimization, or way to off load them to the cloud. This has made my computer useless. My desktop files won't even show on the screen, my mail starts and quits, my browser says I need to delete sites I'm not using but there are only 31 of them saved. Why is this such a hard problems to get solved?

[Re-Titled by Moderator]