speed up / slow down

you should speed up your work ,or you will not finish it on time .

he slowed down his car .

he kept speeding up his car ,which was dangerous

the plane flew higher and higher / lower and lower .

he raised / lowered hight of the flight .

speed up / slow down

you should speed up your work ,or you will not finish it on time .

he slowed down his car .

he kept speeding up his car ,which was dangerous

the plane flew higher and higher / lower and lower .

he raised / lowered hight of the flight .