Responsive design not working with any SEO Plugin

Hi,

it would be so great if anyone can help me.
I tried yoast plugin and also “All in one” to optimize the page for seo. Regrettably the something seems to be wrong with the mobile version when one of the plugins is activated (and only then!). As I am not an expert but trying to solve everything by myself maybe somebody can tell me if this is an issue because of the theme? when I check the mobile design via Customizer everything seems to be fine but actually when checking it via phone it looks very different (much smaller ect.). And also when I check it with the google mobile friendly test it’s not optimized.

*arg*

Greets

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