Learn Portuguese (Portugal): Eu penteio-me em frente do espelho.

In European Portuguese, pronoun placement is strict. In a simple affirmative sentence like this one, the reflexive pronoun (me) attaches to the end of the verb with a hyphen. This is one of the main differences from Brazilian Portuguese, where you will often see the pronoun before the verb.

The English translation says "my hair", but where is the Portuguese word for "hair"?

There isn't one! The verb pentear-se is reflexive, meaning the action reflects back onto the subject. Literally, this sentence says "I comb myself." In Portuguese, it is naturally understood that you are combing your hair, so you don't need to add the extra words for "my hair" (o meu cabelo).

The infinitive of the verb is pentear, so why is the "I" form spelled penteio with an extra 'i'?

Verbs that end in -ear (like pentear or passear) have a slight spelling change in the present tense to match how they are pronounced. For the eu, tu, ele/ela/você, and eles/elas/vocês forms, you add an 'i' before the verb ending. Therefore, pentear becomes eu penteio.

Why does the sentence use do instead of de in em frente do espelho?