It looks as if you have fixed the problem with the arrow to go to the bottom of the page.

To keep the menu on one line, you need to use a smaller font, shorter menu items, or change the padding/margins for each item. You have to make a choice as to what you want it to look like.

Keep the menu simple though. It might be better to have submenus on the pages where you land from the main menu.

@henrythe-stocksorg copy over header.php into your child theme if you haven’t already

Look for the following section of code in header.php

<?php if ( has_nav_menu( 'top' ) ) : ?>
			<div class="navigation-top">
				<div class="wrap">
					<?php get_template_part( 'template-parts/navigation/navigation', 'top' ); ?>
				</div><!-- .wrap -->
			</div><!-- .navigation-top -->
		<?php endif; ?>

Move it above the following line of code

		<?php get_template_part( 'template-parts/header/header', 'image' ); ?>

Then in the Appearance->Customize->Additional CSS area you can use the following

.navigation-top {
	position: relative;
	font-size: 10px;
}

@chelseaedson0056 it is typically better to start your own topic for support, however you should be able to control the menu font using the following in Appearance->Customize->Additional CSS

.main-navigation li {
	font-size: 15px;
}