sich verschlechtern
to worsen
To become worse; to move into a more negative state.
Sein Gesundheitszustand hat sich über Nacht leider verschlechtert.
Unfortunately, his health condition worsened overnight.

to worsen
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to worsen
To become worse; to move into a more negative state.
Sein Gesundheitszustand hat sich über Nacht leider verschlechtert.
Unfortunately, his health condition worsened overnight.

The verb 'verschlechtern' (to worsen) is derived from the adjective 'schlechter' (worse). The prefix 'ver-' here describes the process of changing toward a worse state.
Die Qualität ist jetzt noch schlechter als vorher.
The quality is now even worse than before.
This verb has two important uses: 'sich verschlechtern' (to worsen, reflexive) means that something becomes worse on its own. 'Etwas verschlechtern' (to worsen something, transitive) means that someone or something actively makes a condition worse.
Das Wetter hat sich plötzlich verschlechtert.
The weather suddenly worsened.
In the reflexive form 'sich verschlechtern' (to worsen), typical subjects are impersonal things such as 'die Lage' (the situation), 'die Situation' (the situation), 'das Verhältnis' (the relationship), or 'der Gesundheitszustand' (the health condition).
Die wirtschaftliche Lage im Land hat sich weiter verschlechtert.
The economic situation in the country has worsened further.
to improve
'verbessern' and 'verschlechtern' describe opposite developments. With 'verbessern', something gets better, for example quality, health, or a situation. With 'verschlechtern', something gets worse or someone makes something worse. Both words can be used with an object or reflexively: you improve something, or something improves. In the same way, you can worsen something, or something worsens.

Durch den starken Regen verschlechtert sich die Sicht auf der Straße.
Because of the heavy rain, visibility on the road is getting worse.
Wir haben den Service vor dem Termin noch verbessert.
We improved the service before the appointment.