the theme nicely displays the new wordpress standard MOSAIC galleries on desktop
however there are several bugs in the display of the same gallery on AMP
It seems that the problem is not with our theme. Our regular theme view for every screen sizes the mosaic gallery automatically detect the scree size so it gets fit but for the AMP view the mosaic gallery will not still having same sizes as the desktop view.
Did you take support from the AMP plugin or mosaic gallery plugin main authors?
If not please consider taking support from theme and let us know.