Thanks for replies,
this is a some kind of solution but I have two more questions:

1) The first large image on the top is heavily cropped in the height. How Can I increase this value ?

2) I have two Masonry Galleries there (both in one single full width column) Images below the big picture (linked to the youtube video), are in the second Masonry Gallery. Now I have 2 columns there, how can I change it to 3 columns?

http://mapme.lh.pl/cinetic2/portfolio/polish-film-festival/

unfortunately it did’t change anything :/