I will be staying in Shenzhen and want to travel to Foshan in the morning and return in the evening.

At Shenzhen Luohu Bus Station, take an early bus to ur destination. The first bus leaves at 07:10 and the frequency is 40min. You will arrive in 2.5h. For the return trip, take a bus from FS Bus Station and the last schedules are 17:30, 18:10, 18:50, 19:00, 19:30, 20:10 and 20:50 for your reference.