Airport Extreme? More like Airport Extremely slow!

Hi!

I'm using a MacBook Pro (Retina, 13-inch, Mid 2014)

with 10.10.3 and I've been paying for 250 mbit/s fiber broadband since December-ish, but I haven't been able to appreciate the full speedyness because

1. My MacBook doesn't have an ethernet connection

2. I haven't been able to afford a good router until now.

But I scraped up some money, bought an Airport Express (which was promised to be able to send wi-fi up to 300 mbit/s) and hoped that would do the trick. IT DIDN'T. Got around 60-90 mbit/s speeds on bredbandskollen.se (which is the most trusted Swedish speed tester). Went to the mac store, splurged and exchanged it for a new Express and also an Airport Extreme, to compare and see if I got a wonky copy of the Express the first time around. If the new Express wouldn't work, I was sure that this magnificent and sleek white tower would be able to provide me the hyper-speeds i longed for. ALAS. I got the same speed with the Extreme as with both of the Airport Expresses, around 60-90 mbit/s.

I live in small room (13 square meters) in a students corridor and was hoping of maybe sharing the network with my neighbours if the speed was good enough, but now...

• There's nothing wrong with the cable or the broadband, I've checked by connecting the cable directly to my friend's computer. Also tried with cable via Airport Express to my friend's computer, which also gave 200-250 mbit/s, so no problems there.
• I've tried two different Airport Expresses and one Airport Extreme and they all gave around the same speeds.
• I've moved the Airport around (as much as my small room permits it) with no direct changes in results.
• I have moved around the corridor and tried the speed on varying distances (since an Apple Care-guy said I might be sitting too close to the airport) but without results. Once (1) I got 251 mbit/s, a few steps outside of my room, but when I tried in the same spot again it was down to 60-90 once more.

  The signal doesn't extend decent speeds very far out into the corridor, but that could be because of the thick walls in this old building, I guess.

So, what's up?

Is there anything else I can try out? Could the problem lie with my MacBook? Should I then settle for the cheaper Express? Or abandon my dear Apple and try out one of those ugly, alien-tech-looking routers the other brands offer? Should I give up and cry? I have until June 2nd to return the Express, the Extreme, or both. Please help me!

Thank you in advance, and sorry for this wall of text!

I'm really at loss...

P.S. To be honest, I don't think I actually need the 250 mbit/s. It was just a price difference of €5 between 100 and 250 when I signed up, so I went for the 250. More mbit per € so to speak... And now I'm just annoyed that I pay for this super-fast broadband that doesn't come through, you know? Sigh.