Learn Portuguese (Portugal): Tu não és português.

In Portuguese, to make a sentence negative, you simply put não directly before the verb. Unlike English, you don't need extra helping words. So, 'you are not' translates structurally as não és (not are).

When do I use tu instead of você?

Tu is the informal 'you' in Portugal. You use it with friends, family, children, and peers in casual situations. If you were in a formal setting or speaking to someone older, you would use formal address, such as você, o senhor, or a senhora.

Why is the verb és instead of é?

És is the specific form of the verb ser (to be) that always matches the pronoun tu. If you were using the formal 'you' (você), the verb would change to match it: Você não é português.

Would the word português change if I said this to a woman?

Yes. Adjectives for nationalities must match the gender of the person they describe. If you are speaking to a woman, the masculine português changes to the feminine portuguesa.