Unable to operate.

I waited, waited to write this review ... and finally, after many unsuccessful attempts, I decided: WiFi repeater that does not. Worse, he even managed to crash my Box (of SFR) several times, my phone could not find any WiFi network.
My box is located upstairs, this repeater is connected to the ground floor, just down the stairwell (and I even tried several times to connect the close of the box) .. .and nothing.
Two options: either this unit is actually faulty or it is the victim of a perfectly inadequate instructions (and the manufacturer's website is useless ...).
If ever I succeed one day to make it work, I will give my opinion and most importantly, what to do to make this miracle happen!