What's the average game duration? I've limited time to play, and would like to know if it would be feasible to go online.
Depends what you are playing, either single player or mutliplayer. of course in single player you can go for more than a dozen hours just for one game, but for multiplayer, 1-3 hours (no clue cause I rarely play multiplayer)
Is there an active community I could join (newb friendly then), preferably composed by european players, so I could enjoy compatible timezones and better connections?
Not really since this is a small game.
If so, is it using any tools to facilitate game scheduling, like Steam?
What do you mean scheduling?