Some of your questions are related to basic WordPress usage.
I have added phone number and email in header, widgets in blog sidebar, footer menu.
Header type can be chosen in “Elvyre options -> Header -> Style”, portfolio type in “Elvyre options -> Portfolio -> Category page style”, blog style in “Elvyre options -> Blog -> Blog Layout”.
The shop options are just Woocommerce pages which are used when creating a shop.
The thick scrollbar is available on demo theme only.
For more information please check out the theme documentation.