How do you answer como esta?

If someone asks you "Como esta?" then it means "How is he/she?" You may be confused with "Como estas" wich means "how are you?". You would respond by saying
Bien (sounds like: Byen) meaning "good"
Mas o menos (sounds: moss oh men-ose) meaning "so-so"

mal (sounds:mall) meaning "bad"

Just make sure you use a Spanish-sounding accent