For the first time we open gallery menu bar and images from it is hidden.
As we push to navigate we instant see navigation arrows and small pictures on down of page.
Problem is that these small pictures do not disappear and if I have many pictures in gallery all my mobile window are filled by these small pictures and I cannot see normal image.
If we close gallery and open again, auto hide do not works.
if i understand you right, you do not want the little preview images at the bottom of the screen.
Due to the large number of images in your gallery, these little thumbnails cover up the full image on mobile devices, which makes the prev/next arrows unusable.
To disable these preview images, go to the backend, edit the gallery and switch to the tab 'Gallery info settings'.
Set the option 'Display Infobar' to No and save again.
Now, theses thumbnails will no longer be displayed.