Experiencing some issues with the header on mobile devices

Hello! I wanna report some issues that I have experienced running my website with this theme: Issue number 1. I uploaded a video for the header of my website. On the "Personalize the theme" section it was working flawlessly, I even changed the view to see how the website would look on other devices, and still, I was able to see the video. But when I run the website on my mobile phone, the header doesn't show up: You can only see a big white space and no sign of the video. Issue number 2. Noticing this, I disabled the header of my website. I was shocked to realize that, after doing so, on my mobile phone, the main menu does not work, so as a user I do not have the power to move around the website. I was even more shocked as I discovered that the menu does work on other sites of the website except the main page. Issue number 3. Now, trying to get creative to solve this problem, I tried to find on the code of the theme the section where I can change the size of the header (specifically the height of it). My idea was to upload a picture as my header, small enough to be "invisible" but that would allow me to solve the issue number 2 (as there would be a header that would allow me to get the access of the main menu). I tested all this issues on other mobile devices. All of them show the same problems. I'm sorry for not being able to add some links for reference, the website isn't public yet. I would appreciate having some feedback as soon as possible. Thank you for your time. Ariadna.