There are total 3 tasks.
Task 1: Regarding convert a current tab to drop down menu, I must suggest you to make the drop down from scratch level will be much easy rather than converting an existing tab to drop down, I just remove the code for the Tab, 'case studies', and will make the drop down.
Please let me know if you wish to enable hover on dropdown menu?
-Need to add a class 'dropdown'
-Add button
-Position Dropdown content
-Dropdown content hidden by default
-Add dropdown-content, link etc
-If hover needed, change color of dropdown on hover
-Show the dropdown menu on hover
-Change background color of dropdown button when content is shown
Task 2: Same as task 1. In this case, also confirm me if you need hover?
Task 3: Regarding scroll bar, please confirm me whether you are looking for horizontal scrolling or vertical scrolling or need both?
-Need to set the position of the scroll bar by limiting it left & right
-Need to add width parameter to CSS
As I supposed to work in an existing coding, after implementing the new code with this, there may be few issue arise. But don't worry, I will solve the issues.
Kindly share your existing website URL, I need to check the website, need to view the exact position of the drop downs, Scroll bars etc and also need to noticed which other menus, features are related with the menus.
Anyway, please open your PMB & let me know your convenient time to discuss further. I am waiting here for your prompt response.