In Microsoft Word, you can do this by enclosing the text you want to be conditional inside an "IF" field, and using a document property such as "Category" to control it.
If you want a "With German" resume and a "No German" resume, then you might have the following in your document:
{IF {DOCPROPERTY Category} = "With German" "Fluent in written and spoken German."}
Then, when you want the resume to include the German content, go to File and change the Category property to With German (This is case sensitive.)
Note that you need to press CTRL-F9 to create a field. Just typing the curly brackets will not work. Also note that the conditional text needs to be in quotes.
To avoid having random extra lines in your document, put the field on the same line as the paragraph of regular text that comes after it, and include a hard return inside the quotation marks in the field. For example:
Standard Resume Content
{IF {DOCPROPERTY Category} = "With German" "Fluent in written and spoken German."
}Another paragraph of standard resume content.
becomes
Standard Resume Content
Fluent in written and spoken German.
Another paragraph of standard resume content.
when the category is "With German" and
Standard Resume Content
Another paragraph of standard resume content.
when the category is anything else.