How to use Jiayi ten-thread sewing machine?

The sewing machine of Jiayi 10 line is not so good. It looks like a lot of functions, but it won't work the first time. I always jump the wire and want to return it. The seller refused to give it to me, saying that it was because of my improper operation, but he didn't want to repair it for me, and he kept struggling with the freight. I was very angry. I spent money on a toy. Never buy this shit product of Jiayi again.