Thanks.
The umbrellas are different for the left and the right player. The panther on the left has only three fields for flowers and this is why the umbrella can bash back thrown things of the right player. (You can see that the umbrella icon is different for the two players)
Whereas the right player only has to hold the protector, the left player has to smash F-Button in the moment a snail passes by. Although this is more difficult, the snail changes direction and is thrown back on the field of the koala on the right ;)
So, it is correct when the umbrella closes on the left directly after it was opened.