Learn Hardcore Greek: Διψάω μετά το πάρτι, γιατί μίλησα πολύ. - I am thirsty after the party, because I talked a lot.

δ = voiced “th” as in this (not like thin).
ψ = “ps” as in laps.
γ before ι/ε/η/υ is a soft “y”-like sound; γιατί starts like “ya”.
ρ is a tapped r.
Accents show the stressed syllable: διψάω, μετά, πάρτι, γιατί, μίλησα, πολύ.
In casual speech, verbs in -άω (like διψάω) may sound like two syllables (δι-ψά-ω) or almost like διψά; both are heard.

Why is there a comma before γιατί?

In Greek, a comma normally precedes γιατί when it introduces a reason clause, just like many English writers do before “because” when the reason is an independent clause. If the reason clause comes first, you usually put a comma after it:

Γιατί μίλησα πολύ, διψάω.

Also note: the Greek question mark is the semicolon (;) so Γιατί; means “Why?”

Does γιατί mean both “why” and “because”? How do I know which one it is?

Yes. Context and punctuation tell you:

As “why”: Γιατί διψάς; (Why are you thirsty?)
As “because”: Διψάω, γιατί μίλησα πολύ. (I’m thirsty because I talked a lot.)

Why is Διψάω present but μίλησα past? Is that okay?