HVAC not working properly

Hi everyone, I’ll be super quick about this since I’m already pretty annoyed at what’s going on.

My girlfriend and I moved into our place in December, specifically a second story apartment. We didn’t have a problem with this during the winter but we’ve recently been having issues with our AC. It barely feels like it’s working and, with it constantly going, has sky rocketed our energy bill (280 bucks) and has barely done what it’s suppose to do. We’ve contacted maintenance and they’ve come by to “clean it out” but that only helps a little bit.

For example, it’s fine if the outside temp is 75. But the moment it hits a certain temp (like 85) and we set it to 75, it can barely get under 78 degrees.

We just recently put in a portable AC unit into the apartment but we’re still trying to figure out how to maximize its usefulness. In the midst of this heatwave, does anyone have any advice on how to handle this with management? Or how to get this portable AC to work in the way we need it to? (Only place we can put it is in the kitchen, which is a bit far away from the bedroom)

We’d greatly appreciate any advice. Thank you!!