Im Waschsalon um die Ecke höre ich oft, dass viele Leute wegen einer Mieterhöhung umziehen müssen.

Im is a contraction of in dem.

Here, in describes a location: the speaker is hearing this in the laundromat, not moving into it. With location, in takes the dative case, so:

• in dem Waschsalon → im Waschsalon

If it were about movement into the place, German would use the accusative:

• Ich gehe in den Waschsalon. = I go into the laundromat.

So in this sentence, im Waschsalon is dative because it answers where?

Um die Ecke is a fixed expression meaning around the corner.

It uses um + accusative, which is why you get die Ecke here. Even though there is no literal motion around a corner in the sentence, this expression is idiomatic and commonly used to describe something nearby:

• der Bäcker um die Ecke = the bakery around the corner
• der Waschsalon um die Ecke = the laundromat around the corner

So you should learn um die Ecke as a set phrase.

In a normal German main clause, the finite verb goes in second position. That is the standard V2 rule.

The sentence begins with a prepositional phrase:

• Im Waschsalon um die Ecke = position 1

Then the finite verb comes next:

• höre = position 2

Then the subject follows:

• ich

So the structure is:

• Im Waschsalon um die Ecke | höre | ich oft ...

This is very common in German. If the sentence started with ich, then it would be:

• Ich höre oft im Waschsalon um die Ecke, dass ...

That version is grammatically possible, though the original sounds more natural because it foregrounds the place.

Dass with double s is a conjunction meaning that.

It introduces a subordinate clause:

• ..., dass viele Leute ... umziehen müssen.

Das with one s is usually:

• the neuter article the
• or a pronoun meaning that

Compare:

• Ich weiß, dass er kommt. = I know that he is coming.
• Das Haus ist groß. = The house is big.
• Das weiß ich. = I know that.

A helpful trick: if it introduces a whole clause, it is usually dass.

Because dass introduces a subordinate clause, and in German subordinate clauses the finite verb goes to the end.

So:

• Main clause: Ich höre oft ...
• Subordinate clause: dass viele Leute ... umziehen müssen

Inside that dass clause, the verb material is sent to the end. Since there is also a modal verb here, the verb cluster at the end is:

• umziehen müssen

This is one of the most important word-order patterns in German.

German often uses quantifiers like viele, wenige, einige without an article.

So:

• viele Leute = many people

That is completely normal. You do not need a word like die here.

Compare:

• Viele Leute kommen zu spät.
• Einige Studenten wohnen hier.
• Wenige Kinder verstehen das.

Also note that Leute is a very common everyday plural noun meaning people. There is no singular Leut in normal modern usage for this meaning.

Wegen means because of or due to.

Traditionally, wegen takes the genitive case, and that is what you see here:

• wegen einer Mieterhöhung

Mieterhöhung is feminine, so:

• nominative: eine Mieterhöhung
• genitive/dative feminine indefinite article: einer Mieterhöhung

In everyday spoken German, you may also hear wegen with the dative, especially in some regions, but the more standard written form is the one used here.

So this sentence uses the standard pattern:

• wegen + genitive

Mieterhöhung is a compound noun:

• die Miete = rent
• die Erhöhung = increase

Together:

• die Mieterhöhung = rent increase

German forms compounds very freely, and the last part determines the gender. Since die Erhöhung is feminine, die Mieterhöhung is also feminine.

That is why the sentence has:

• wegen einer Mieterhöhung

It can mean either, depending on context.

1. umziehen = to move house / relocate
2. sich umziehen = to get changed / change clothes

In this sentence, because of wegen einer Mieterhöhung, it clearly means:

• to move house

So:

• Viele Leute müssen umziehen. = Many people have to move.

If you want to say change clothes, German often uses the reflexive form:

• Ich ziehe mich um. = I’m changing clothes.

Because in a subordinate clause with a modal verb, German usually places the verb cluster at the end, with the main infinitive first and the modal infinitive last:

• ..., dass viele Leute ... umziehen müssen.

So the order is:

• umziehen = main verb
• müssen = modal verb

This is the normal pattern.

In a main clause, the modal becomes the finite verb and moves to second position:

• Viele Leute müssen wegen einer Mieterhöhung umziehen.

But after dass, the verbs go to the end:

• ..., dass viele Leute wegen einer Mieterhöhung umziehen müssen.

Good question. Umziehen is indeed a separable verb.

In a simple main clause, separable verbs split:

• Ich ziehe morgen um.

But in infinitive form, the verb stays together:

• Ich muss morgen umziehen.

And in this sentence, umziehen appears as an infinitive because it depends on the modal müssen:

• ..., dass viele Leute ... umziehen müssen.

So it stays as one word: umziehen.

Oft means often and functions as an adverb of frequency.

In the sentence:

• Im Waschsalon um die Ecke höre ich oft, dass ...

it modifies höre: the speaker often hears this.

German adverbs like oft can move around more than in English, but not completely freely. For example, these are all possible, with slight differences in emphasis:

• Ich höre oft im Waschsalon um die Ecke, dass ...
• Im Waschsalon um die Ecke höre ich oft, dass ...
• Oft höre ich im Waschsalon um die Ecke, dass ...

The original version sounds natural because it first sets the scene, then gives the frequency.

Because Leute already means people as a plural noun.

So:

• viele Leute = many people

This is one normal German way to say people in everyday language.

A few related words:

• die Person / die Personen = person / persons
• die Leute = people, folks

In everyday speech, Leute is extremely common and often sounds more natural than Personen, which can sound more formal depending on context.