Do you pay before or after you sit down and eat?since its an all you can eat buffet do you pay as soon as you walk in? Are their any other fees that might be charged?

After

After you finished eating. Unless you order any special drink or food, there will be no charge other than tax.

After, quite easy.

Pay after. Order by scan the code on the table. Some food need extra cost are on the menu. No hidden fee from what I can see.