The most common German word for “improvement” is “Verbesserung” (f.), which can also mean “correction”. Alternatives are “Optimierung” (f.) (“optimization”/“optimisation”/“optimation”), “Fortschritt” (m.) (“progress” or “advance”). The verb for “to improve” in German is “verbessern” (which also means “to correct”). The opposite “to worsen” is “verschlechtern”, and the noun is “Verschlechterung” (f.) (“deterioration”, “degradation”):

– “Du hast dich wirklich verbessert!” – “You’ve really improved (yourself)!”
– “Ich muss deine Sprache immer verbessern.” – “I always have to correct your language.”
– “Die Verbesserung der Sicherheit ist sehr wichtig.” – “Safety improvement is very important.”
– “Wir machen viele Fortschritte.” – “We’re making a lot of progress.”
– “Die Lage hat sich verschlechtert.” – “The situation has worsened.”