EX3700 inconsistent wifi as extender from Technicolor gateway router (at my landlord's next door)

First, I just got off the phone with a dude in India whom I thought was Netgear tech support, but apparently it was a company that shows up in the Google search very slyly making themselves look like Netgear, so I allowed him to login remotely to my network and see what was going on, but then when he was at the root of the problem, he tells me that it would be $250 to do all this work that "needs" to be done. We'll see if that was a foolish thing to do.  

I'm no tech guy, but I can usually figure things out when shown what to do. So, the Indian guy said that neither the modem/router or my machine have firewall activated, (which they don't) and that someone would need to set it up correctly and then make sure the firmware is up to date on all devices. He said that is the reason my EX3700 is unable to keep a consistent connection.  Right now, it is working fine.  Usually what happens is that when I come home or get up in the morning, the connection is fidgety and nothing I do will keep the connection, but then after 30min to and hour (give or take) the connection seems to come back and stay for a while, sometimes not giving be problems for days.  But, inevitably, this starts happening again. Either or both of the green Router or Device light will be off, sometimes just the Router light will be red.  I can see the wifi 2.4g _ext network (I set it to Modem->5g->Extender->2.4g->devices on FastLane, the other way wouldn't work at all) on both my iPhone or my iMac, but either it will not connect or will work for a couple seconds, then drop it again.  Sometimes it wants to take me to the mywifiext.net page, which does nothing.  The useless Apple network diagnostics in the system preferences will sometimes re-establish the connection, but often it will not.  

I have spent the last two years at this place with crappy internet, (the Technicolor gateway router is about 40-50 ft from my cottage at my landlords) sometimes it was the old extender, sometimes it was the ISP (Hawaii, third world countries have better internet) and when I replaced the old Netgear extender with this one, I was hopeful that the issues would be reduced.  They weren't, they just took a slightly less annoying form.  

So, I am at a loss as to what to do next.  I am able to access the Technicolor admin page, I could turn on Firewall protection there and on my machine, I even did so momentarily after I talked to the Indian dude, but it didn't seem to make any difference, and from what he said, I needed an "expert" to get my EX3700 to function as it ought to. Didn't see any firmware update options there either. Firmware on the EX3700 is up to date. Any takers? Thanks in advance.