Styling not working

Hello
I am using popup with a contact form.

I am trying to style the contact form that is inside the popup with the parameters that i can select from the GUI, but it doesnt seem to do anything, I want to add white background to the \”input fields\” and change button color, but no matter what I do, nothing changes.

I can edit some CSS code, but I am not that good so I dont want to mess around to much.

I dont know what the problem is and it is really frustrating.
Can someone please help?