Wifi/firewall issues

Let me start out by stating that I don't have that much knowledge about wifi network issues and all that good stuff.

The wifi in my apartment has been terrible recently. Wifi comes free with my apartment so I don't pay for it or have control over the account. In hopes that I'd improve my wifi connection, I bought a WIFI extender from NetGear. It was only like $40 so I figured I'd give it a shot.

Well I was having trouble setting it up so I called customer support. The guy gets on my computer remotely and shows me that my firewall failed or something and a lot of people are using my wifi which is preventing my extender from connecting to the router. He was saying stuff like dont use online banking on this network because people can see what you're doing.

He tried to get me to buy a firewall from netgear but I told him my situation with my landlord controlling the wifi. I told him that because (a) it's true and (b) I wasn't sure if he was trying to rip me off or something. I didn't want to drop $100-$200 on the spot without getting a second opinion. Plus, I don't even know I could get a firewall installed on my network since I don't have control over it.

So first, is this guy messing with me?

If not, is there anything I can do about it besides tell my landlord? I'm sure he's not interested in dropping a few hundred on this.