@colettedurand, the problem is that there are so many menu items that when the browser is at a certain width, the menu items wraps to another line and makes the header bigger. Right around 1050px, the menu wraps down below the level of the search field because the search field element is defined first. Then around 910px, the Special Events menu item wraps down to a third line. I don’t know how you want to fix it, you can’t really make the header narrower. You can try adjusting the line height of the menu items and search icon by adding a rule like this:
#site-navigation .menu li,
.search-icon,
.search-icon i {
line-height: 34px;
}
By the way, I don’t know if you’ve noticed or not, but your mobile menu button doesn’t work. The reason is that it looks like you’ve manually added some Google Analytics code into your post or page, and you’ve included the blank lines within the script. Whenever you include any sort of scripting code, you have to make sure there are no blank lines or else WordPress will try to insert some HTML paragraph tags, and that screws up not only the script that you are trying to execute but any other javascript (including the script which processes the mobile menu button). Since you’ve already added the Google Analytics code using a plugin, you should remove the code that you manually entered so your mobile menu button will work.
Also, when making changes, you shouldn’t be making any changes to any of the theme files by going to Appearance → Editor (like changes to style.css). The next time you update the theme, your changes will be lost. The suggested way to make theme changes (that can’t be done using the Customizer or the theme options) is to create a child theme or use a Custom CSS plugin if you are just making CSS changes.
Finally, you should post questions related to the Himilaya theme in the Himilaya support page or Theme Grill’s support forum. This is the support forum for the Make theme, and you shouldn’t jump in on someone else’s question, especially if the theme is different. Thanks.