Change css of a script that so it does not break current layout

Hello Freelancers, I have bought a specialised website. It is offered in a SAAS solution, so I don’t have access tot the source code. The WYSIWYG editor doesn’t touch any added html/javascript code, so I can make modifications by adding my desired code to the page editor. I have bought on envato market a script that adds html5 tabs to the content area. This script breaks some of the html of my website. I am looking for a person that can modify my envato script, so that it does not break the layout in my SAAS website. The script I bought at Envato market (on request I can give you full access tot his source code) [login to view URL] My site without the tabs: [login to view URL] My site with the tabs: [login to view URL] As you can see the tekst is smaller on a some parts. For example: - The login/shopping-cart in the header is smaller with the tabs in my site - The tekst in the dropdowns are smaller with the tabs in my site. - Going to the tab “Veelgestelde vragen” the accordion titles are smaller that they should be. - The text/titles in the blue bars are smaller with the tabs in my site. - The text in the green buttons are smaller with the tabs in my site. I have added a pdf that shows the current situation and the endresult, how it should look like. The only way to achieve this is to make some changes to the tabs script.