I'm very surprised about your bad review: all the times I spoke on phone with your boyfriend, who was the intermediary as he is italian, and I asked him if everything was ok and if there was any problem, he always answered that everyting was ok, no problems.
I didn't specify that the apartment is on ground floor because I didn't imagine this could be a problem, as it is not on the road but in a quite courtyard. If this is so important for you, don't forget to ask this information to the host before booking. The ventilation inside a small apartment is of course absent, as you said, if you keep all the windows (living room, bathroom and kitchen) closed; and of couse after shower and cooking a lot of steam is produced and it create a "tropical situation" with oll the window closed, not only in a ground floor apartment.
Moreover in this period a bit of humidity is present in most of houses of Milan, as the temperature is lowering and the heating system is not working in all the town by law till the half of October.
Anyway noone before or after you complain about that.
I'm really sorry for your disconfort, but next time when you have any problem try to speak with the host, maybe she/he can help you to solve your problems.