How to collect data and headers for non blank cells in a row in Sheets

I cannot find a solution to my problem:

I have a sheet with ~290 rows and ~80 columns. The first row and column are fixed/header.

I would like to collect non-blank values and their header into row B.

I've tried to search for solutions, but I'm not as good at excel, so I cannot wrap my head around most of the advice that I've found.