Slider hidden behind menu on mobile / tablet

Hello,

A client of mine who is using the free version of this theme has a couple issues regarding the top slider as well as post titles getting hidden behind the menu on various devices.

Domain in question: https://zontatoronto.org/

Have attached a few photos displaying the problems. 2 from my iPhone:

and 1 from the client’s 13″ MacBook Pro:

The position of the slider and post title gets changed depending on the device and is hidden behind the navigation. The odd part is most mobile simulators I’ve used to test the website display it as it should be, with the slider docked below the navigation. However, when loading the site on the actual device, it displays with the slider hidden behind the navigation. The only testing suite I used that displayed the issue accurately was mobilizer, but this is because they are using the actual devices.

I’d like to have the slider / post title / content docked below the navigation. I was going to add some margin to the slider or menu, but since the positioning changes on a per-device basis I’d have to write dozens of media queries. If there’s a global fix for this that would be wonderful.

If any more information is needed I’ll be happy to provide it. I didn’t setup this theme initially, so it’s possible some changes had been made by the last person who worked on it.