iPad view – removing grey background – spacing – i dont find the problem

hello! gerne auch auf deutsch…

i am struggling with a gutter row and my elements. i do not find any clue where i can remove the grey background which is generated from “main content” settings. but i want it just transparent. also the spacing of the objects is completely unclear – i do not find the problem, why spacing is ok in the top row, but gets more and more in the following entries.

thank you for any help!

have a nice day, stefan.