Place it immediately after the question about how you are, as the direct answer in the scene, then follow it with Ceeday Huh for a confused double-take or Oh My God Wow when friends react to the answer.
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This is a brief spoken Spanish phrase, lasting about one and a half seconds, in which a voice calmly says “Estoy bien.” The delivery is plain and unhurried, giving it a reassuring, matter-of-fact feeling that suits a simple answer rather than a dramatic reaction. It works as a quick, friendly way to say you are doing fine.