i have a standard 60 day visa, what happens if i overstay for about 2-3 weeks?
You will have to pay a fine (NT$1000?) and you will get a stamp in the back of your passport that will make it hard for you to get another visa to come back to Taiwan. Don’t overstay if you can possibly avoid it - unless you have no intention of ever coming here again.
If you have a standard 60 day visa, and you don’t want to be blackbanned for a year, go and sign up at a language school. This will allow you to legally stay here for an extra month, or if want, even 4 more months.