erhöhen
to increase
To raise something in its amount, value, intensity, or degree; to make it larger.
Das Unternehmen wird die Gehälter um drei Prozent erhöhen.
The company will increase salaries by three percent.

to increase
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to increase
To raise something in its amount, value, intensity, or degree; to make it larger.
Das Unternehmen wird die Gehälter um drei Prozent erhöhen.
The company will increase salaries by three percent.

The verb is derived from the adjective 'hoch' (high). The inseparable prefix 'er-' often expresses that a state is reached or an action is carried out successfully. So 'erhöhen' (to increase/raise) literally means 'to make higher'.
Die Stadt plant, den Lärmschutzwall zu erhöhen.
The city is planning to raise the noise barrier.
'Erhöhen' (to increase/raise) can be used transitively or reflexively. When a person or institution actively makes something larger, you say 'jemand erhöht etwas' (someone increases something). When something rises on its own, you say 'etwas erhöht sich' (something increases).
Die Zentralbank erhöht den Leitzins.
The central bank is raising the key interest rate.
If you want to state the exact amount of the increase, use the preposition 'um' followed by an accusative. This pattern is very common.
Der Vermieter hat die Miete um 50 Euro erhöht.
The landlord increased the rent by 50 euros.
You can tell whether a physical or an abstract increase is meant from the object. Abstract nouns like 'Preise' (prices), 'Gehälter' (salaries), or 'Geschwindigkeit' (speed) point to the figurative meaning, while concrete nouns like 'Mauer' (wall) or 'Deich' (dike) suggest the literal meaning.
Der Hersteller hat die Preise für alle Modelle erhöht.
The manufacturer has increased the prices for all models.
to improve
'erhöhen' and 'verbessern' can both describe a positive change. The difference lies in the focus: 'erhöhen' means that an amount, a value, or a degree becomes larger. 'verbessern' means that something gets better or gains higher quality. Learners may confuse the words because more is sometimes also better. But a price can increase without that being good. And a text can improve even if no number becomes larger.

Die Firma erhöht im nächsten Monat die Preise.
The company is increasing prices next month.
Adam verbessert seine Präsentation mit klareren Beispielen.
Adam improves his presentation with clearer examples.