A sheet's size depends on the mattress, not the bed frame. Measure the mattress, width then length, and compare here.
3-piece: a sheet, a fitted or flat sheet, two pillowcases. 6-piece: the same plus a top sheet and two extra pillowcases. Go for 6-piece if you want to change sheets without washing the same day.
The fitted sheet clips under the mattress and stays put at night. The flat sheet folds over the duvet. Both come in Full size, at the same price or close to it.
Combed cotton breathes, the right pick for the hot season. Satin glides and shines, more for gifting. Velvet keeps you warm, for harmattan nights.
Cotton at 40°C, satin and curtains at 30°C, dry in the shade. Keep incense and oils out of sunlight. Orthopedic pillows: wash the cover only.