Hi Frank,
I have tried all options mentioned in wordpress for sorting based on sorting options.This is the best option currently we have.
Reason it do not come in first row is there are keywords used in other courses as well.

https://developer.wordpress.org/reference/classes/wp_query/#order-orderby-parameters
There is a string related thing relevence however it makes it worse due to sorting it based on these factors
*‘relevance‘ – Order by search terms in the following order: First, whether the entire sentence is matched. Second, if all the search terms are within the titles. Third, if any of the search terms appear in the titles. And, fourth, if the full sentence appears in the contents.*

If you want further explanations I can discuss over all. 