I’m OK, thank you. Estou bem, obrigado/a Eshtoh baym[ng], Obrigahdu/a – lit. “I am well, thank you.”  This is perhaps the most common response to the above question.  For ‘thank you’, men say ‘obrigado’, women say ‘obrigada’ (regardless of whether the person they are talking to is male or female).*
 
I am fine Estou óptimo/a Eshtoh ohtimu/a – note that the ‘p’ in ‘optimo’ (fine) is virtually silent (the Brazilians spell it without a ‘p’).  Again, whether to use ‘optimo’ or ‘optima’ depends on your own gender.
 
Is everything OK? Tudo bem? Toodu baym[ng]? – lit. “everything well?”  Note:  This is probably the most common greeting in Portuguese - it is used much more frequently than ’como está?’.
 
Yes (everything is ok) Tudo [bem] Toodu – lit. “everything [well].”  The ‘bem’ is optional when replying to the above question