1), 2) To edit footer contact go to Static Blocks > Edit Footer Burger static block and edit content using WPBakery builder https://xstore.helpscoutdocs.com/article/47-static-blocks
3) Provide screenshot for better understanding. You can use Lightshot tool for these purposes.
4) Go to Appearance > Menus > create/edit mobile menu with items you need and don’t forget to check menu location – Mobile menu https://gyazo.com/2e502e5dd596d6051b111dcf9acc8676
5) If you don’t change the template files of the parent theme you won’t lose your changes after the update. Anyway, we would recommend you to do the backup before proceeding with any update.
Go to Static Block > edit footer burger block and choose the menus what you want to show http://prntscr.com/nx45nj
At this moment the same menu is chosen in settings of both elements just like an example.