Track height

Hi,
I am new to Trax and to planning tools for railway. I am having difficulties adjusting the height of a track section.
Whenever I try changing the height of selected (and connected) tracks to a level, lets say -35mm, I always end up adjusting only the first of the selected tracks.

Can someone please help me with a "step-by-step" guide how to adjust the height.

Thanks a lot,

Martin