I have a back tooth extract 2day one dentist refer me to serg, saw an other said it hard one but he can remove it, I'm scared?

It's normal. It's normal to be somewhat scared. Discuss this further with the surgeon who will be actually treating you. He\she can discuss the options for ensuring that you are completely numb and will not feel anything.
Normal. It's normal to be apprehensive before any surgical procedure. it seems y9ou are seeing an Oral Surgeon who is the most qualified specialist to address your problem. Discuss your concerns with the Oral Surgeon who will give you knowledgeable answers to all of your questions.