No longer usable after a few hours use

The assembly of the trimmer is easy. Mir is already noticed that the cord was adhered to the first coil and additionally cracked. That was not really to use later. The engine has made limp after about 1 hour. The device then goes from easy. After a short delay, I could use the trimmer again ... but of course, not very long. The intervals were shorter. Then I complained about the device. I noticed that the air vents are provided very far down. That is conceivable stupid, because this area very quickly clogged with grass. This could also be the cause of the problem be? Almost 2 weeks ago, the input of the device has been confirmed and since then I have only one packet mark (!) And receive otherwise no Feedback. I advise on the device. At most easiest for inserts the trimmer could suck.