Qatar is totally safe country. Don't worry, whoever tells you it is dengerous has no clue what they are talking about.. For some people the words "Middle East" are already dengerous.. and here is definitely not less safe than in Serbia.
Just come over, see your future employer... my advice, try to get a good sense of him, what kind of person he is.
Since he will be your employer and your sponsor, you will be totally depending on him (which personally i wouldn't like, but it is your choice).. so at least try to make a conclusion what kind of person he is, it is very important.. Don’t be shy to ask the questions, you might learn a lot about the person based on his answers, try to watch him, how he treats other people around..