Also, radio signals can bounce on obstacles, they don't just get absorbed. Look at how radars work as a real-life example.
Closer to the ceiling than in the middle of the room might help by having part of the signal bounce around.
after further testing, my wifi signal strength was better when I first got the router, so was the throughput,
I placed just the router upstairs(with modem connected through Ethernet) and although the signal strength went up, the signal downstairs droped to 75 dBm, and was pretty much nothing..
I moved the router back to where it was and tried the settings displayed by another user, but a lot of issues arose ;
1- on 40mhz, the max speed becomes 450Mb but the actual speed tests show 4Mb upstairs and signal strength dies out in the furthest room sto the left and right of the front of the house.
2-putting back to 20mhz gets me around 40Mb upstairs and 10 - 17Mb ish in the furthest room sto the left and right of the front of the house
3-turning beamforming on in the 2.4ghz gives me slower speeds, the further I go from the router, upstairs. (so im keeping it off)
4-at one point the router just died, although the light were blinking and wifi was broadcasting,no connections were coming through (internet,)
I couldn't access the router or anything , I had to unplug it for 30 seconds twice to get things back working.
so yeah, not too sure what to do, at first the router was amazing, now it seems like its slowly dying...