Having trouble editing site, probably stupid questions…

Our site was built away from wordpress, and then migrated over by a third party who intergrated CMS. We’re now having trouble doing some editing.. If anyone can give us some pointers, that’d be awesome!
We’re new to wordpress, slowly getting our heads around it. Think the problems might be due to Advanced Custom Fields, but not sure

Site is http://www.markov.com.au

Main issues are:
-We want to resize the main container, including the menu bar
-We’d like to put some content on the RHS side of screen, outside the menu/content container
-We want to add an img to the menu bar
-Would like to create some new pages that aren’t children (therefore don’t show up in the menu table) but are still able to be linked
-We would like to set maximum height for content page (See pages under “Eat”. The content box resizes itself, and allows way too much space after last line of text)

If anyone has any ideas we would love to hear them,

Thanks!