Hello,
I saw the screenshots you attached.
1) Please try adding the following Custom CSS in the Global Custom CSS area under Theme Settings >> Custom CSS.
.mc4wp-form-fields input[type="email"] {
background-color: black;
}
2) The white space is due to the margi that is added to the columns please edit the row and try removing the margin values.
Screenshot for Clarification: https://ibb.co/StsBxC0
3) Your screenshot is not clear enough to understand what you require. Please provide a relevant screenshot of the specific area to check it myself and help you out accordingly.
Regards.
Xtemos Studios