index/match function as vlookup for 2 columns

Hello there !

I've searched throughout the forum, did find some answers to my question and think I've learned how to use index/match formula.

The thing is, there is still sth missing in my formula - it's really hard to explain it, so I will be really grateful if you can take a look at my working file - I bet that it won't take you more than 5 sec to see what is wrong with it

So what I wanna do is get the value from column "C" in 1st sheet and place it in column "C" in the 2nd sheet only if values from both column "A" and "B" from 2nd sheet are the same as column "A" and "B" from 1st sheet - sounds a bit complicated, but looks very simple in the file

Thanks a lot in advance