Ich suche meinen Gürtel, bevor ich das Haus verlasse.

Because Gürtel is the direct object of suche, and suchen takes the accusative case.

• Nominative: mein Gürtel = my belt (as the subject)
• Accusative: meinen Gürtel = my belt (as the object)

Since Gürtel is masculine (der Gürtel), the possessive changes in the accusative:

• der Gürtel
• ich suche meinen Gürtel

This is one of the first case changes English speakers often notice in German.

In this sentence, the case marking shows up on the word meinen, not on Gürtel.

That is very common in German. The noun often stays the same, while the article or possessive word changes:

• mein Gürtel
• meinen Gürtel

So even though the case changes, the noun Gürtel remains unchanged here.

Because all nouns are capitalized in German.

So:

• ich is not capitalized unless it starts a sentence
• Gürtel is capitalized because it is a noun
• Haus is capitalized for the same reason

This is a basic spelling rule in German.

Because bevor introduces a subordinate clause, and German normally separates subordinate clauses with a comma.

So the sentence is divided like this:

• Main clause: Ich suche meinen Gürtel
• Subordinate clause: bevor ich das Haus verlasse

The comma is required.

Because bevor is a subordinating conjunction, and in German subordinate clauses the conjugated verb usually goes to the end.

Compare:

• Main clause: Ich verlasse das Haus.
• Subordinate clause: bevor ich das Haus verlasse

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

German normally requires each clause to have its own subject if the subject is meant explicitly.

So even though the same person is doing both actions, German still says:

• Ich suche meinen Gürtel
• bevor ich das Haus verlasse

English does the same thing here: I look for my belt before I leave the house.

So the repeated ich is completely normal.

Because verlassen means to leave and usually takes a direct object in the accusative:

• das Haus verlassen = to leave the house

German also has:

• aus dem Haus gehen = to go out of the house

Both can work, but they are structured differently:

• Ich verlasse das Haus.
  Direct object with verlassen
• Ich gehe aus dem Haus.
  Prepositional phrase with aus

So das Haus verlasse is correct because verlassen does not need aus.

No. Verlassen is not separable.

That is why you say:

• Ich verlasse das Haus.
• bevor ich das Haus verlasse

You do not split it into something like lasse ... ver.

This can be confusing because many German verbs with prefixes are separable, but ver- verbs are usually inseparable.

Suchen means to look for or to search for.

It does not mean to find.

So:

• Ich suche meinen Gürtel. = I am looking for my belt.
• Ich finde meinen Gürtel. = I find my belt.

That distinction is important because English speakers sometimes mix up suchen and finden.

Yes, but the normal, neutral order is:

• Ich suche meinen Gürtel.

German allows other word orders for emphasis, as long as the conjugated verb stays in the second position in a main clause. For example:

• Meinen Gürtel suche ich, bevor ich das Haus verlasse.

That version emphasizes meinen Gürtel, but it sounds less neutral than the original.

So the sentence you were given is the most natural everyday version.

Verlasse is the first-person singular present tense form of verlassen:

• ich verlasse
• du verlässt
• er/sie/es verlässt
• wir verlassen
• ihr verlasst
• sie/Sie verlassen

In the sentence, ich is the subject, so verlasse is the correct form.

Yes. Haus is a neuter noun:

• das Haus

In this sentence it is in the accusative, but for neuter nouns the article das stays the same in nominative and accusative:

• Nominative: das Haus
• Accusative: das Haus

So even though the case changes because it is the object of verlasse, the article does not change form here.