Ok, I've checked everything I could and I've seen that when a cable was in power line the led light on router become orange (not green like others). Then I found a long cable (CAT 5E) and connect it directly to my PC (the cable went over the couch in our living room ) and the led light went to green, the speed was 192 mbps. So, perfect!
So, the next plan was to convince my wife that the cable around doors won't look so bad She was and is still ok with it!
Hooray, I'm on cable without power line now and my speed if perfect!