You can easily customize the website with your own custom CSS code. We suggest using the custom.css file instead. By default custom.css file doesn’t exist, you have to create a new file inside /css folder of the template. 

Remember that CSS cascades in reverse, meaning rules that appear later always take precedence over rules that appear earlier. So any CSS applied to a separate sheet will override the page’s default code. This method should help you to add custom design changes that stay exactly how you want them to, no matter what new updates roll out.

Note! Please do not edit the template.css or any other css file from the Helix template framework. The reason being that all of your changes will be overwritten by a template engine. Instead, we suggest using custom.css file where you can override the default CSS code created by our team.

Please read also that blog post: https://www.joomshaper.com/blog/which-line-of-css-i-have-to-edit-code-inspector-in-action