can i apply online and how fast can i get it and what documents should i send along?

As a Chinese, you need to get a HK-Macau Pass from your local police station. Then you will be given endorsement on the pass which tells you how many times you can go to HK and how long you can stay each time. It takes about 5 to 20 days. I think you need to contact the police station and see if there is a rush service.