Question about Samsung QE75Q60T

Exactly the distances of the threads are 400x400mm

Yes, of course, it shows a wide variety of models in the matching accessories.
I just mounted this TV on the wall yesterday with the TITAN BTI 8060 wall bracket. Very easy to do and looks great.
Here is the link to the product: Titan BTI 8060 (Wall, 85", 50kg)