GridBox : issue with Tablet and Phone

Hello Team,
I have a problem that I can't solve.
I placed a form in a blog post, as usual.
This form displays correctly on PC and Laptop but I have display problems on smaller screens, from landscape tablets.
I checked the post layout, I only have one column.
For all devices, I checked that the number of columns was indeed 12
Can you help me to resolve this problem if it pleases you?
The address site is visible on the joined screenshot
It's quite urgent thank you

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