I know this is probably a silly question, but I couldn't find it Googling neither by searching this site.
I'm wondering if, to receive notifications from new answers, it is enough to upvote a question, or so I have to mark is as favorite?
You have to star it in order to be notified. Upvoting a question simply means you think it was a well-written, well-researched and/or interesting question. Favoriting it, on the other hand, means you are interested in the question and you wish to keep track of its activity.