Ich benutze nur mildes Shampoo, weil meine Haut empfindlich ist.

Because ich takes the 1st person singular form of the verb.

The infinitive is benutzen = to use.
In the present tense:

• ich benutze
• du benutzt
• er/sie/es benutzt
• wir benutzen
• ihr benutzt
• sie/Sie benutzen

So Ich benutze means I use / I am using.

Because Shampoo is neuter: das Shampoo.

Here, mildes Shampoo is in the accusative case because it is the direct object of benutze. After nur, the adjective still has to agree with the noun.

With an adjective before a neuter noun and no article in front, German uses the ending -es here:

• mildes Shampoo
• compare: kaltes Wasser
• compare: frisches Brot

So:

• das Shampoo → neuter
• direct object → accusative
• no article → adjective shows the grammatical information
• therefore: mildes Shampoo

Yes. In standard German, it is usually das Shampoo.

That is why you get:

• ein mildes Shampoo
• das milde Shampoo
• ich benutze mildes Shampoo

The gender matters because it affects articles and adjective endings.

Because Haut is feminine: die Haut, and in this sentence it is the subject of the clause meine Haut empfindlich ist.

In the nominative feminine, the possessive form is:

• meine Haut = my skin

Compare:

• meine Haut = nominative / accusative feminine
• meiner Haut = dative or genitive feminine
• meinen is used with some masculine plural forms, so it does not fit here

So meine Haut is correct because my skin is the thing that is sensitive.

Because weil is a subordinating conjunction. In German, a clause introduced by a subordinating conjunction usually sends the conjugated verb to the end of the clause.

So:

• main clause: Ich benutze nur mildes Shampoo
• subordinate clause: weil meine Haut empfindlich ist

Normal main-clause word order would be:

• Meine Haut ist empfindlich.

But after weil, it becomes:

• weil meine Haut empfindlich ist

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

Weil means because.

Yes, you could also use denn in a similar sentence, but the grammar changes:

• Ich benutze nur mildes Shampoo, weil meine Haut empfindlich ist.
• Ich benutze nur mildes Shampoo, denn meine Haut ist empfindlich.

Difference:

• weil introduces a subordinate clause, so the verb goes to the end: empfindlich ist
• denn does not change normal word order: ist empfindlich

Both can mean because, but weil is extremely common in everyday German.

Because empfindlich is being used as a predicate adjective, not directly before a noun.

In German:

• before a noun, adjectives usually take endings:
  empfindliche Haut = sensitive skin
• after verbs like sein, werden, bleiben, adjectives usually stay unchanged:
  Die Haut ist empfindlich.

So in meine Haut empfindlich ist, empfindlich has no ending because it comes after ist in function, even though the verb is moved to the end by weil.

Nur means only.

In this sentence, it modifies mildes Shampoo:

• Ich benutze nur mildes Shampoo = I only use mild shampoo

Its position is natural in German: it comes before the part it most closely relates to.

Compare:

• Ich benutze nur mildes Shampoo. = I only use mild shampoo.
• Nur ich benutze mildes Shampoo. = Only I use mild shampoo.
• Ich benutze mildes Shampoo nur im Winter. = I use mild shampoo only in winter.

So word position can change the emphasis.

Yes. Benutzen and verwenden can both mean to use.

• Ich benutze nur mildes Shampoo.
• Ich verwende nur mildes Shampoo.

Both are correct.
Very generally:

• benutzen is very common and everyday
• verwenden can sound slightly more formal or neutral in some contexts

For this sentence, either works well.

Because all nouns are capitalized in German.

So:

• das Shampoo
• die Haut

But adjectives and verbs are not capitalized unless they begin the sentence:

• mildes
• empfindlich
• benutze

This is a standard rule in German spelling.

Yes. German present tense often covers both ideas:

• I use only mild shampoo
• I’m only using mild shampoo

German does not usually need a separate form like the English present continuous.
So Ich benutze nur mildes Shampoo can be understood from context as either a general habit or something happening now.

Because German normally uses a comma before a subordinate clause, and weil introduces one.

So the comma separates:

• main clause: Ich benutze nur mildes Shampoo
• subordinate clause: weil meine Haut empfindlich ist

This comma is not optional in standard German spelling.