Hi Gutshot
When editing the header that you imported, you can select a block >> add Element called Joomla: module or position as you wish and load the languageswitcher module there.
About the sticky header, you can add this class for the header: t4b-sticky-yes it will help to make the header sticky when scrolling down
For show/hide header when scrolling up / down, I will pass to the dev team for further review.
Regards