Any recommendation in Tainan, plan to for 5 days

I think for a five-day trip in Tainan is a long time to travel. You can choose to other places near Tainan after you finish traveling in Tainan.
In Tainan, you can go to Taiwan Confucian Temple, National Museum of Taiwan History in Anping District and Fort Provintia in Western Central District. Besides, if you do not go shopping, you will be very regretful and it has the largest night market in Taiwan that you need to enjoy. Taiwan is also very famous for its Buddhism, so there are many temples in Tainan. You can choose go some of them.
After you finishing visiting in Tainan, you can choose to go to Taoyuan for a visit by taking the High Speed Rail.