Excuse me for bothering yet please. You said that You would have few species in mind right. It would make my choice way easier if You can listed at least 4,5 of these, which You think might be a good pick, so that I would have at least bit of idea before going to expo. Planning to buy some books aswell. Thank You in advance
Questions are never a bother. That's the main point of this kind of forum- education
Unfortunately, while I have a generalized knowledge of medium species parrots, my in-depth knowledge base for species recommendations is more with large parrots. There are many members more qualified than I to make some suggestions regarding medium parrot species so I'd take my "advice" below regarding medium species with a grain of salt
Green cheek conures are generally well thought of as good "first birds" and are known for being on the quieter side for parrots. They are also quite common (in the US) and affordable, leaving you with more money for cage/toys etc... LOTS of GCC owners on here to chat with if they seem appealing to you.
Indian ringneck parakeets are fairly popular medium parrots. I personally sublet in a home with a blue IRN and took care of him on occasion for the owners. He was a shy bird and loud enough to give my large amazon a run for his money. Very snuggly with and strongly bonded to his owner. That, of course, is my limited experience with that one bird and may not be characteristic of all IRN's. One of our members, SilverSage, breeds IRNs and if they seem appealing to you, she would be my top pick to ask questions about them and get firsthand info from a reputable breeder who knows what they're talking about.
Quaker parakeets are another medium parrot species that are common first birds. Don't know much about them myself. Several other users have them though. They are illegal to own in several US states due to the potential to become invasive species. You'd be wise to check local laws where you live as the EU tends to have even tighter regulations than we do over here.
Poicephalus have a reputation for being a bit nippy but are also known for having big personalities and being more independent. The most common POI species (in the US) are Senegal parrots. Not as popular as conures or IRNs, but they're worth looking into if a more independent/less velcro personality appeals to you. Personally, I'm more fond of birds who don't need to be glued to you every second, but that's just me.
Pionus are closely related to amazons and if their personalities are anything like their larger cousins, they would probably be a top choice for me personally to research if I were looking for a medium size parrot. Not too common to find them though over here. They are also known for being a more independent species.