Will i be able to get my 5 month work VISA?

Also I forgot to add that I tried to apply for the work Z through an agency that sent all my documents to the Chinese embassy and in the end I only got 2 month!! In my application I asked for 6 month. So now that they've already 'approved' me, is there anything I can do to change it to 6 month?

I am afraid that it is difficult to change it. You need to apply for a new one if you don't want the old one. But I think you may not get a new one with longer duration. The agency is powerful. If they can't get a longer one for you, you will have little chance to get one by yourself.