A person used force (F) , shown in figure to move a load with...

First a force is used to move the body when it has to be more than the static friction. Then the body starts moving and is getting accelerated. Then
suddenly the force is decreased to match the kinetic friction. The body then moves with a constant velocity. Force $>\mu_s \cdot N$. Constant acceleration, velocity increases proportionately with time. Then suddenly force applied is just equal to $\mu_K N$. It is just sufficient to cancel friction. Whatever be the earlier maximum velocity attained will be continued.