My MacBook Pro memory was full so I deleted a bunch of files and now it won't start and I get strange errors. What do I do?

First, I'll admit that I know nothing about computers. My MacBook Pro was being very slow so I checked the memory and it was low so I started deleting a bunch of unknown files. Suddenly, my Mac shut down. At first when I went to start it, it didn't recognize my password. So I turned it off, and tried to restart. This is where the weird stuff happened. It tried to start, but after a few seconds, I got a very long error message that included the words "debugging" and "panic." Now my Mac just keeps cycling between that screen and the reboot screen. I think I totally screwed it up! What to do?