Learn the theory
"Fine/Fijn" is a word that is used a lot in both English and Dutch. But watch out, because there is a slight difference. If you have been answering "fijn" to tell how you are, you should read on.
"Fijn" can't be used to express your mood or current state! It would translate as "nice" or "pleasurable". Let's just look at some examples.
I have had a nice weekend. Ik heb een fijn weekend gehad.
This is a comfortable/nice bed. Dit is een fijn bed.
I am fine. Ik ben oké.
Just like in English "fijn" can also mean something finely, thin.
I have fine (thin) hair. Ik heb fijn (dun) haar.