Ubuntu 20.04 keeps freezing before login

I am using 20.04 and my laptop keeps freezing before the login. What can I do now? I am having this issue from yesterday. There was a tty terminal available but there is nothing now. It all started when I installed a program called picom and after that my i3wm froze. I tried restarting my laptop but I couldn't get any desktop environment running. And now there is no login either.