Learn Portuguese (Portugal): Tudo bem, obrigado.

In Portuguese, you do not need a verb to say "everything is fine". The phrase Tudo bem literally translates to "everything well", and it acts as a complete sentence on its own.

Does Tudo bem also mean "How are you"?

Yes! It is the most common way to ask how someone is doing. You just change your voice to make it a question: Tudo bem? And the other person can reply with the exact same words to say they are fine: Tudo bem.

Does everyone say obrigado to mean "thank you"?

No, it depends on the gender of the person speaking. If you identify as male, you say obrigado. If you identify as female, you say obrigada. Since the speaker here uses obrigado, we know he is male.

Why do we use tudo here instead of todos?

Tudo means "everything" as a general concept, which fits this sentence perfectly. You use todos when you are talking about specific groups of people or things, meaning "everyone" or "all of them".