Are you allowed in this situation to enter the level crossing, if the red light has already gone out, but halfbarriers are yet the be fully raised?

Why?

The half-barriers in the video are still rising. You must not enter until they are fully raised, even if the red lights have already gone out. Before moving onto the crossing, you must also check that no train is approaching.

art. 28 ust. 3 pkt 1 Prawa o ruchu drogowym