To much space above form in twenty fifteen

Hi, been tweaking a twenty fifteen theme and having problems with to much space above a form. I go to firebug and it lists this.

*, *::before, *::after {
    box-sizing: inherit;
}

Researched it and tried this with no luck.

form {
    box-sizing: content-box;
}

I know basic css but this it out of my league. It seems to be forcing the form box to the left and baseline but even if I could remedy that there would still be to much space below as well as above it.

Don’t really understand the basics on this and it seems to be a global thing so afraid anything I do to fix this form will screw up the rest so was wondering if there is anything I could do to affect this form only. The form starts out like this if it’s any help.

<form method="GET" action="https://www.amazon.com/gp/aws/cart/add.html">

Any help is much appreciated ??