Optimizing Javascript of Modal Window Function in a Joomla Website

I am a practitioner for mental health in Germany. I am able to express myself in English, but I prefer to work with freelancers, who speak German fluently - just in order to prevent misunderstandings, which can be very expensive or at least time consuming and frustrating. Actual I am creating a new website on Joomla 3 platform. My main focus is optimizing UX and focusing visitors, when they have chosen what they are interested in. Therefore I need modal windows, in which I present video clips, audio clips or articles from Joomla content. It is important, that this content can be presented flawlessly on nearly all recently used class of devices like mobiles, tablets and desktops! I already have setup a Joomla website and tried JCE-mediabox without success on mobiles. Then I came across with the Joomla-Plugin RokBox, which is a free extension from https://rockettheme.com. This does a great job, but has some severe flaws. You can watch JCE-mediabox and RokBox in action on my experimental website at [login to view URL] (Homepage only). I am not bound to JCE or RokBox, but open for other solutions, which will do their job in stable and reliable manner. Another task is the mobile menu. I have chosen a free menu "The Grue Menu", which is working OK on desktop but is squirky on mobiles. Either you can optimize "The Grue Menu" for me or you can insert another Joomla mobile menu, which will show up a similar function and design and is also a free menu. As you have access to my already existent website and as you can check the required functions, you can more easily calculate your job. The job should be done and finished completely at the end of August 2020. I prefer German freelancers to avoid language misunderstandings.