Do I need visa? Do i need to pay taxes? If not, is there any??

Minl, how long will you stay there? If you want to stay longer than 14 days, you need to apply for an entry permit in advance. However, as you are not married with your girlfriend, I'm afraid you can't apply for the dependant entry permit. So it you don't work or study in HK, it's difficult to get a long-term entry permit. As for taxes, I'm confused about it. Taxes for what? Would you explain?