My masters project is very unclear, is it realistic to expect me to complete it successfully?
Welcome to the wonderful world of research! You're describing what research is like: nobody really knows the answers, so nobody can really give you concrete guidance; nobody really knows what will work, so the only thing to say is "try it and see what happens". It might sound optimistic, and in some sense it's a good optimism, because no matter what happens you've discovered something new.

So relax and do your best. If you try something and it doesn't work, explain why it doesn't work to your supervisor. If you get stuck, also let your supervisor know. Your supervisor cannot really spell out what to do for you every time; it's quite possible he'll say "okay, we're stuck. What do you think we should do next?" and you can try thinking of something (don't worry if you fail; after some time he'll probably think of something himself).

Finally don't worry about what happens if the project turns out to be unfeasible or not work as expected. Nobody can guarantee beforehand if the project is going to work as expected. You're likely to be graded over your work, not your results. If your supervisor had given you a project that turned out to be more complicated than expected, he'll undoubtedly factor that into the grade, as well.