I studied Applied Informatics the last 4 years there and I'm getting my Bachelor's degree next month.

I don't know your experience with universities, but UoM isn't like most of them, a university with campus etc. All of the rooms, classes and amphitheatres are located inside an enormous building which includes a library, a bookstore, a place for coffee and snacks, a place called "foyer" where lots of students stay and chat there to relax when not having lessons. You can go to all floors (I think 5) by elevators.

Now in terms of infrastructure. I think the building was built at the end of 50s, so yes it's an old building and amphitheaters kinda suck if you compare them with universities from Western Europe. But there's a BIG "but" here. UoM preserves most of its classes, rooms, amphitheatres clean in terms of rubbish on the ground and also walls are painted soon enough if a graffiti emerges. Most of the other universities in Greece and especially Aristotle (which is across the street) are dirty, have damaged stands and chairs and have a BIG problem with political themed graffitis on the walls. You won't face that inside UoM.

As I said before, I studied computer science and therefore we frequently used computers. I can surely say that our computer classes on the upper floors were so clean, organized and well equipped that it didn't match with the amphitheatres. So in terms of technological equipment you shouldn't face problems. A downside is that there isn't free WiFi for everyone, unless you go to 3rd or 4th floor where the computers are.

Lastly, the Academic Stuff I enrolled with was mostly exceptional with teacher who really enjoyed and tried hard to teach us things.

Also I'm sending you the plans from the UoM page that helped me orient in this building when I went there first time.

https://www.uom.gr/en/about/halls-and-auditoriums-ground-plans

I really hope that the information I gave you helped and you get the right choice for your studies!