Is there a fast bus from Shanghai to Suqian and how long would it take?

Yes, you can take it from the General Bus Station and arrive at Suqian directly.
The bus schedules are 07:00, 08:30, 09:30, 12:50, 13:50, 17:00, 17:50 and 19:00. The ticket fare is CNY 136 or CNY 176 per person. Generally speaking, the trip takes 5.5 to 6 hours. Hope helpful!