Mobile rendering?

I like many things about this theme, but one I’m having a really hard time with is how it renders on mobile devices. On my iPhone and iPad (using Chrome and Safari):

– the header image looks squished together
– the top hamburger menu, when clicked, displays all main items PLUS sub-group items, all in one long list
– generally, post layouts occasionally render in strange ways depending on the size of images in the post

Am I doing something wrong, or are these issues that might be addressed in another version?