@vwirth I agree with @Eric it would be very beneficial to learn how Responsive code works before making customizations that may affect it.
Just like HTML, CSS, or any code you can’t just add or remove things without there being an effect…..unless you know what you’re doing. This goes for any theme you use, regardless which theme it is.
If you’re using a plugin, make sure it works properly so it doesn’t conflict with anything else.
I looked at your site and the responsive code seems to be working at the moment. Good job by the way, it’s looking good 馃檪