My professor threatening to complain about me to Principal and parents, if I don't help him with his tasks. I am afraid. I don't know why he doing this. What do I do?

Do what you feel is right and comfortable. Even if you are afraid of the outcome that he will complain to your principal and family, if you explain to them your situation and your feelings they will understand.

Tell everything youself to parents about the teacher they will help you as much they can so don't be afraid

I hear you. You're afraid and confused about what to do. It would be easier to accept advice and to assume that it is correct, but you are the expert on your experience and your life. Ultimately you are the one who will bear the consequences whether good or bad for your choice. I believe that people are able to grow and make their own decisions responsibly if they are given the right conditions. Talking with an empathetic listener who is authentic may be the ticket to getting unstuck. Talk through the options until you decide on one that fits you.