It is not your navbar that is too long. It is the container in top-section and than the div with the class:“top-wrapper”. Put an overflow-x hidden on your “top-section → container” or on the top-wrapper itself.
It sounds like the navbar might not be responsive. Try adding CSS media queries to adjust the width for mobile and tablet views. You may need to use max-width or adjust padding/margins for smaller screens to ensure it fits properly.