I was washing the upper part of my leg with kurr water and it touched a pipe that was najis so when I made it tahir with qur water, the water obviously will flow to the lower part of my leg and then on to the bathroom floor.

So does that mean that the lower part of my leg and the bathroom floor have become najis too ? (Through the water)

No. The lower part of your foot didn't become najis neither the floor.
because you made paak with kurr water