What is the minimum distance for a MAXtream connection between two CPE210? Is it better to just use "normal" wifi repeater mode if the distance is about 50 meters?

Hi, i'm from Morocco, i bought a TD-W8961N(EU)V4 from local market. I have 2 problems with it: 1. A Network problem: I configured my modem/router with my ISP info and it's connected and all fine, BUT,