Du siehst schick aus.

Schick means something like stylish, smart, elegant, or well-dressed. In Du siehst schick aus, it is a compliment about how someone looks.

It does not usually mean handsome or beautiful in the broad sense. It is more about someone’s appearance, clothing, or overall style.

Because the verb is aussehen, which is a separable verb.

• infinitive: aussehen
• in a main clause: Du siehst ... aus.

So the prefix aus- separates from the main part of the verb and goes to the end of the clause.

Examples:

• Ich sehe gut aus.
• Du siehst schick aus.
• Er sieht müde aus.

That is normal word order for a separable verb in a main clause.

In German main clauses, the conjugated part goes in the usual verb position, and the separable prefix goes to the end:

• Du siehst schick aus.

But in some other structures, the verb stays together:

• infinitive: schick aussehen
• subordinate clause: ..., weil du schick aussiehst.

So the aus at the end is a grammar feature, not a special emphasis.

Because the subject is du, and the verb must be conjugated to match it.

The verb aussehen uses the stem seh- / sieh- in the present tense:

• ich sehe aus
• du siehst aus
• er/sie/es sieht aus
• wir sehen aus
• ihr seht aus
• sie/Sie sehen aus

So with du, the correct form is siehst.

Yes. Du is the informal word for you, used with friends, family, children, and many people in casual settings.

If you want the formal version, you say:

• Sie sehen schick aus.

So the choice between du and Sie depends on the relationship and level of formality, not on the grammar of schick aussehen itself.

Because schick is being used predicatively, not directly before a noun.

After verbs like sein, werden, and aussehen, adjectives usually do not take adjective endings.

Compare:

• Du siehst schick aus.
  predicative adjective → no ending

• Du trägst ein schickes Kleid.
  adjective before a noun → ending needed

So schick stays in its basic form here.

Yes, but it is not exactly the same.

• Du bist schick = You are stylish / fancy / dressed nicely.
• Du siehst schick aus = You look stylish / You look smart.

Aussehen focuses on appearance: how someone looks right now.
Sein describes a quality more directly.

In many everyday situations, Du siehst schick aus sounds more natural as a compliment.

No.

• sehen = to see
• aussehen = to look / to appear

So:

• Ich sehe dich. = I see you.
• Du siehst gut aus. = You look good.

Even though they are related in form, they mean different things.

Yes, it is quite common, especially in spoken German. It sounds natural and friendly.

Depending on context, other common words are:

• gut = good
• hübsch = pretty
• schön = beautiful / nice
• elegant = elegant
• stylisch = stylish

But schick has a nice sense of being well-dressed or fashionable.

Yes, like many compliments, it can be sincere or sarcastic depending on tone, facial expression, and context.

For example:

• sincere: someone is dressed nicely for an event
• sarcastic: someone is overdressed, oddly dressed, or messy in a situation where the speaker is joking

The grammar stays the same; only the tone changes.

A simple pronunciation guide is:

doo zeest shik ows

A few notes:

• du sounds like doo
• siehst has a long ee sound
• sch sounds like English sh
• ch in schick is just part of sch, so schick sounds like shik
• aus rhymes roughly with English house without the h

In a subordinate clause, the separable verb usually becomes one word again:

• Ich finde, dass du schick aussiehst.
  = I think that you look stylish.

Notice the difference:

• main clause: Du siehst schick aus.
• subordinate clause: ..., dass du schick aussiehst.

This is a very common pattern with separable verbs.