Grading animation

is it possible to animate a grade? for example, I want to gradually decrease luminance during a specific clip. how can I achieve that?

Sure. Use keyframes. But, you have to do this in the numeric entry area, not with a curve or slider. For example, in PI room, set a keyframe (ctrl 9) where you want the animation to start, move the playhead to where the animation should end, set another keyframe and adjust the luminance value in the master gain entry.

All the rooms can be keyframed, so you could do the luminance ramp in PO if that works better for you. Click and drag on a keyframe to slide its position. Ctrl 8 to adjust interpolation, Crtl 0 to delete. You can also add more than one correction per keyframe, so you could for example have the luminance shift and ramp colors as well in the advanced tab.