Understatement: nicht + the opposite
British English is famous for understatement: a bit of a problem for a disaster. German is generally more direct, but it has one productive pattern: deny the opposite. nicht gerade billig means expensive, nicht ganz unproblematisch means problematic. The point is clear, and the speaker sounds measured rather than blunt.
Direct and understated
Das Hotel war teuer.
The hotel was expensive.
Das Hotel war nicht gerade billig.
The hotel wasn't exactly cheap.
Der Plan ist problematisch.
The plan is problematic.
Der Plan ist nicht ganz unproblematisch.
The plan isn't entirely without its problems.
Workplace understatement
Die Präsentation ist noch ausbaufähig.
The presentation could still do with some work.
means: it is weak
Da ist noch Luft nach oben.
There's still room for improvement.
Nicht schlecht, wirklich.
Not bad at all.
usually sincere praise
Irony: praise for something bad
Verbal irony says the opposite of what the situation shows. English signals it mainly with tone. German adds grammatical signals that make it hard to miss: the particles ja and mal wieder, an opening Na, and an exaggerated positive word.
Das war ja mal wieder super.
Well, that went brilliantly. Again.
mal wieder: this always happens
Na toll. Jetzt regnet es auch noch.
Oh great. Now it's raining as well.
Herzlichen Glückwunsch, du hast den Schlüssel schon wieder vergessen.
Congratulations, you've forgotten the key again.
Das hat ja hervorragend geklappt.
Well, that worked out wonderfully.
In speech the voice helps: the positive word is drawn out and the melody stays flat instead of rising with real enthusiasm.
Where irony goes wrong
In writing, the voice is missing, and in a business context irony reads as passive aggression. Keep it for people who know you. In a formal email, say the thing directly but politely.
A late reply
Ironic
Vielen Dank für Ihre schnelle Antwort nach drei Wochen.
Many thanks for your speedy reply after three weeks.
reads as an attack
Direct and polite
Vielen Dank für Ihre Antwort. Leider hat sich die Sache dadurch verzögert.
Thank you for your reply. Unfortunately this has delayed matters.
