Visitor Visa Extension

Hey all,

Got a question-how long does it take to process a visa extension? I’ve got a single-entry visitor visa for studying Mandarin that will expire on December 12th, so the earliest I can apply is November 27th. I’m planning on leaving Taiwan to visit family on December 9th and will be back around the 14th. Also, could I convert my visa to multiple-entry? I’d like to get an ARC, so I’d prefer to not get in through the visa waiver (US citizen).