I'm from Austria and would like to move to Helsinki to do a PhD here. I am currently trying to figure out how the standard of living in Helsinki would be for me and was hoping you could give me some advice.

I have learned that the average starting salary is roughly 2200 euros/m gross, but I couldn't figure out how much net salary that would be (my guess is something around 1700/m?) Is it possible with this salary to live a "decent" life in Helsinki? I'd like to live in a flat that's at least 35-40m2 big (no shared flats), preferrably somewhere in or near the center or with good public transportation; I guess that would be around at least 800-900 euros/month? I don't have any expensive hobbies and am not a person who goes out that often, but I'd like to afford going to cafes or having lunch somewhere every now and then without having to worry about my bank account. In my memory the prices for groceries in the supermarkets are rather expensive, I read that it's about 100 euros/week, is that realistic for a single person? Also, I don't really know about the finnish insurance system. Do I have to pay extra for that or is that usually covered by the employer?
As for living, Töölö area would be my dream (yes I know it's very expensive and unrealistic) but I'd also be interested in experiences from any other parts of Helsinki, especially Kallio, Vuosaari or the area around Itäkeskus.
I'd be very grateful if you could give me some advice. Thanks in advance
