Oi Pri, Good: é usado normalmente antes de substantivo. Ex: She is a good student. Well: Normalmente usamos depois do verbo. Ex: She works well. Obs.: Well também é usado para indicar problema de saúde. Ex: John was sick, but now he is well. Foi a explicação do professor Carlos ok. A detalhe good bom, well bem depedendo da oração tem que ser weel não serve good. Ex: This explain is very well. Deu para esclarecer sua dúvida?

Example: How are you? I am fine, and you? I am fine too, thanks.

You can use either as Adrianita mentioned. However being 'well' is more of an answer to asking about your well-being or health in general , while 'being fine or good' is used when asking how you are doing .

You can say I´m fine, I´m well, I´m good. The 3 answers are ok and mean the same