How can I navigate by height?

Question

css

I can’t get flexbox or I don’t understand how to make the navbar height from header to footer. Here is my example of what I was able to do https://jsfiddle.net/hollanditkzn/2c9L13g3/1/

Answer 1

.row {
  display: flex;
}

https://jsfiddle.net/2c9L13g3/3/