How to alter the header and add a top drop-down menu in the Debut theme?

[Lily2020]

Want to change the header and add a drop down menu on top instead of on the side  

how does this work? 
when choosing this theme on the example it showed that it should be possible 

thanks 

[Hardik29418]

Please give me collaborate access of your store to parambabla.soft@gmail.com