Product not conform to its description. Seller bad faith

I bought this TNT with multimedia features for watching TNT and play MKV files - AVI, or 2 functions that are highlighted on the packaging of the box and its description.
Concerning TNT decoder function, no complaints, the picture is good though the colors are oversaturated.
The "Time Shifting" (direct control) at first seems to work well, but the break, the greater the chances of start playback are low. For information, a pause of 5 minutes has resulted in a sound and image shift when resuming playback, and a break of about 40 minutes completely planted the device.
Multimedia side, do not expect to watch encoded videos MKV, they're just playable on this device. From the beginning of the reading, there is a delay between sound and image, and this shift is progressive as and able to play (regardless of file size, test with MKV about 350MB, 700MB and several GB).
So we end up with a gap of over 10 seconds after 10 minutes of viewing ... On and MKV 700MB +, the subtitles are not displayed after several attempts.

This dysfunction (as it is) is known Xeofix, but will not be corrected. The multimedia function is highlighted on the box and in the description, but is not usable and will not be repaired.

Finally, shop side, responsiveness is good, but the bad times as well. According to them, my device is not malfunctioning because it is sold as CI + earth terminal. So they do not accept full refund, but they apply a discount depending on the state of the equipment. For my part, 15 discount for new equipment under the pretext that the plastic film has been removed, the remote control batteries have been unpacked, and the tips of the HDMI cable has been removed.

Added to this is the cost of return ports, outstanding because it is in their cancellation of order and not a return to malfunction.

Result, money lost (stolen?) By people of bad faith (thieves?) And a company that makes false advertising (scammers?).

You do not catch me.