Machine flop - Amazon top!

I treated myself to this machine as beginners won't. I was impressed by all the stitches for a relatively small money. From the outset, the Carina has unfortunately disappointed with an unclean stitch image. My guess, it's up to my "Anfägner-Arts" and I have done something wrong, has not been confirmed to me a professional. I've done everything right, the machine sews simply unclean (upper / lower thread tension are not compatible, to huge thread node and absolute blockade). Then I sent Amazon whopping four months later a complaint. This was processed within half an hour, I was offered a return label sent and three days after returning the full amount was refunded to my account. The machine has very disappointed me and unfortunately I can not recommend the Carina Professional. But Amazon is for me the most customer-friendly company ever!