MrBillieBob

Welcome!
So getting a new (better) router won't help if you just have too many devices in your area trying to talk.
One other thing is how does the extender do it's back haul communication? Is it on Ethernet? Another WiFi Channel? Is it 2GHz or 5GHz?
If you get wifi analyzer for your phone or tablet (there are some in the windows store to.), are there a lot of other routers trying to talk? Are they overlapping? I'm a UniFi guy my self like @seanondemand so I to have something of a skewed view of wifi, since I just have an AP on Ethernet where ever I need one.

I'm a UniFi stan, but it's the Ubiquiti UniFi setup Linus is referring to, and it's rad. I set it up in my home because we've got 50+ devices now including in our yard so being modular and adding APs where I need them makes the coverage crazy good, and the stability is awesome. 
 
It is more work to set up and has a lot more configurability that can be a bit overwhelming, but I'd recommend it to anyone who's a bit tech savvy. I did a writeup on my build-out here
 
Today, I'd recommend someone start out with a UniFi Dream Machine, and potentially one or two APs to extend coverage where you need it, and running ethernet to devices where you want maximum stability, like work machines or media centres.