Could need some help creating a multilanguage website

[vulcan]

I looked at the lang.Merge documentation and found a related post as well but it´s unclear to me.
I want exactly what you mentioned here:

Unclear how to use lang.Merge - How to add language fallback for content

A gap is a “missing translation”, e.g. you have content/about/_index.md – but not content/about/_index.de.md

Do I have to past a code snippet into layouts\work\single.html?