Wenn ich einen langen Text lese, suche ich zuerst die Verben und dann die Nomen.

Because wenn introduces a subordinate clause in German. In a subordinate clause, the conjugated verb usually goes to the end.

• Wenn ich einen langen Text lese = When I read a long text
• The verb lese is pushed to the end because of wenn

This is a very common pattern:

• Wenn ich Zeit habe, ...
• Weil er müde ist, ...
• Dass sie kommt, ...

So the key rule is: subordinating conjunction + ... + verb at the end.

German main clauses follow the verb-second (V2) rule. That means the conjugated verb must be in the second position.

In this sentence, the whole subordinate clause comes first:

• Wenn ich einen langen Text lese,

That entire clause counts as position 1. So in the main clause, the verb must come next:

• suche = position 2
• ich comes after it

So:

• Wenn ich einen langen Text lese, suche ich ...

not:

• Wenn ich einen langen Text lese, ich suche ...

This inversion is very normal in German whenever something other than the subject comes first.

Because Text is a masculine noun (der Text) and it is the direct object of lese. Direct objects often take the accusative case.

So:

• nominative: der lange Text
• accusative: einen langen Text

Both the article and the adjective change:

• der → einen
• lange → langen

This is why you get:

• ich lese einen langen Text

This is because of adjective endings in German.

In einen langen Text:

• Text is masculine
• it is in the accusative
• it comes after the article einen

For a masculine accusative singular noun after ein-/einen, the adjective usually takes -en:

• ein langer Text = nominative
• einen langen Text = accusative

So the ending -en tells you that the phrase is masculine accusative.

Because in German, all nouns are capitalized.

So:

• Text
• Verben
• Nomen

all start with capital letters because they are nouns.

This is one of the most noticeable spelling differences between German and English.

Both Verben and Nomen are plural nouns here:

• das Verb → die Verben
• das Nomen → die Nomen

They are the direct objects of suche, so they are in the accusative plural. In this case, the article is still die, which looks the same as the nominative plural article.

So:

• nominative plural: die Verben
• accusative plural: die Verben

and likewise:

• die Nomen

This is a very common question.

• wenn = when as a conjunction, or sometimes if
• wann = when in a question

In your sentence, wenn introduces a clause:

• Wenn ich einen langen Text lese, ...

That means when/whenever I read a long text.

Compare:

• Wann liest du den Text? = When are you reading the text?
• Wenn ich den Text lese, ... = When/Whenever I read the text, ...

So here, wenn is correct because it connects two parts of the sentence.

Because German normally uses a comma to separate a subordinate clause from the main clause.

So:

• Wenn ich einen langen Text lese, suche ich zuerst die Verben und dann die Nomen.

The comma marks the end of the wenn-clause.

German uses commas in places where English sometimes does too, but German comma rules are generally stricter and more regular.

They are adverbs showing the order of actions.

• zuerst = first
• dann = then

So the speaker is saying:

1. first, I look for the verbs
2. then, I look for the nouns

In the sentence:

• suche ich zuerst die Verben und dann die Nomen

they help organize the sequence clearly.

Yes. Both are first person singular present tense forms.

• ich lese = I read / I am reading
• ich suche = I look for / I am looking for

German simple present often covers both the English simple present and present progressive, depending on context.

So:

• ich lese can mean I read or I am reading
• ich suche can mean I look for or I am looking for

Because wenn is used for repeated, general, or future situations, while als is used for a single event in the past.

This sentence describes a general habit or method:

• When I read a long text, I first look for the verbs...

That is exactly the kind of situation where German uses wenn.

Compare:

• Wenn ich einen langen Text lese, suche ich zuerst die Verben.
  = whenever / when I read a long text

• Als ich gestern einen langen Text las, suchte ich zuerst die Verben.
  = when I read a long text yesterday

So als would not fit the original sentence.

Yes. Nomen and Substantive can both refer to nouns in grammar.

So these are both possible:

• ... suche ich zuerst die Verben und dann die Nomen.
• ... suche ich zuerst die Verben und dann die Substantive.

In many classrooms, Nomen is very common and easy to understand. You may also hear Substantiv in grammar explanations.

Not always. In this sentence, suche is best understood as look for.

• ich suche die Verben = I look for the verbs

German suchen often corresponds to:

• look for
• search for

depending on context.

So here, a natural English gloss is:

• I first look for the verbs and then the nouns

rather than the more formal-sounding I search the verbs.