AirPort Express Connectivity Issues

Hello Apple community!

I have been having some issues with my AirPort Express device. I can connect to it (and it shows up in my AirPort Utility as green), but then I can never surf the web when on it. I thought it was a problem with the original internet at my university, but that is also green (sometimes orange on AirPort Utility). And when I surf on my university wifi, everything works. I wanted to have the AirPort Express just so that I have a safe connection.

Also, my AirPort works when I connect to it via cord. That means the problem is with the bluetooth, right?

Can someone help me please in solving this issue? Is it a problem with my bluetooth connection? Strength of the school wifi? The AirPort device itself? Something completely different?

(I have an early 2015 MacBook Air, using OS X Yosemite 10.10.5 and bought my AirPort in mid-2015, and this happened a few times, but not as bad as now.)