TeraPump TRHD03 Battery Operated 2D Pump with Buzzer

Why does it start beeping and stops pumping after a few seconds?

Great pump; I use it for transferring gsoline into my boat.Is it recommended to flush it after each use?

Can anyone tell me how much liquid this transfers per minute?

Can this pump be used to transfer stain like ready seal ftom a 5 gallon container to a 1 gallon container. ready seal is oil based.