POST GRID // halfthumbleft / mobile devices

Hello, i have a little problem when i use one of my grids on my front page which i have set to  1 column flat / halfthumbleft (100% on desktop /100% on tablets / 90% mobile ).  It looks really great on my desktop, but when i view it on a mobile device, it behaves funny and doesn't look to good ( vertically viewed on my mobile, the thumbnail becomes really small and the excerpt keeps at 50% of the screen, not justified...)   My theme tends to bring everything in one column on mobile devices and i would like it if that grid could adapt as well. Any idea on how i could fix that? Regards.