Are punctual in English and punktuell in German the same?

Here’s the short answer: punctual (English) and punktuell (Deutsch) don’t mean the same thing. This is another example of a false friend. So what’s the difference?

Punctual in English

Punctual is an English adjective for something which happens at the correct or arranged time. Someone who is always on time is punctual, for example. 

     Swiss trains are usually punctual.

In German, punctual would be punktlich.

Punktuell in German

In German, however, punktuell has nothing to do with being right on time. When something is punktuell, it is related to a point or about a specific point. In English, the closest translation is selective or point by point

     Ich stimme deinen Vorschlag nur punktuell zu.

I only agree with some points of your suggestion.

Another meaning for punktuell could be when something is in one or more specific points in time or in a place.

     Nicht das ganze Gemälde wurde restauriert, sondern nur punktuell die schlimmsten Stellen.

Not the whole painting was restored, but only the worst parts of it.

     Nach den starken Regenfällen ist nun nur noch punktuell mit Schauern zu rechnen.

After the heavy rainfall, only isolated showers are to be expected.