Answers

I would suggest calling the original installer and let them buff it out. 

I would call a local company that sells quartz countertops and find a service rep that can come out and handle the repair properly. This will ensure that it is repaired by a professional. First I would call the company that installed the countertop and they may be able to take care of it for you or point you in right direction.

The process of repairing quartz countertop problems and blemishes is a very special skill that involves complicated processes. The painstaking task often requires painting and chip repair so you should never try to fix blemished pieces on your own. In fact, you should leave all of your installation and repair to professionals. If you try to fix them yourself you will doubtlessly be creating more problems for yourself down the road. This can be an expensive and annoying mistake if you constantly have to repair a wrongly installed countertop.