Struggeling with Grid and/or my custom container

Hey guys,

I’m struggeling to have my 12-col grid take up the full span of the parent-container it is sitting in. MY container is set to max 1200px, but when I add children into the grid and click “preview”, it shrinks the grid to center.
I guess this is an issue with my customer container that the grid sits inside; when I set a fixed width of 1200px to the container (as a test) I do not have this grid-shrinking issue, but this would kill the responsiveness of the container :confused:

Can somebody help me out here?

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