Change order notes in checkout of woocommerce, fix menu dropdown

I need to fixes:

1. I need a small change to the checkout page of my website which is woocommerce website. Instead of saying order notes (option) I would like to change this to other words.
Instead of saying notes about your order, e.g. special notes for delivery, i also want to change these words to something else.

2. I need to fix the submenus of my website. for example when I click stickers, a huge submenu pop out and the links CANNOT be clicked. I need this fixed and I want the submenu to be not be big menu, but pop down horizontally as narrow submenu.