Girlfreind problems

So I was dating a girl for like 6 months then I cheated on her and this kid told her about it and I was denying it but 5 days after I cheated I told her the truth and she didnt want to break up but she kept saying stuff that pissed me off so I dumped her...

then I went to the movies with her after we broke up and I started crying because I realized how bad I want her back and she wanted me back but now we are back together but the problem is that she told her parents when I dumped her and now her parents want to kill me and they dont know we are together again and I dont know what to do to make her parents like me again

you need to talk to her parents.
seriously, it will show them you have interest in their daughter and that you care for her. you must also reassure them that what you did was a huge mistake and that you will never do it again.
of course, DON'T DO IT AGAIN.