My mac suddenly restored to what it was about a month ago. How do I get my work back (unback-up) it?

So basically, I restarted my computer because it was extremely laggy. But then, when it turned back on I noticed that my computer did not have anything like the homework and the apps that I recently downloaded. So when I looked into the files, it basically went back in time 😝 like it is what it was 1 month ago. How can I get my things back?

PLZ help