Hide / show fields with conditions

Hello;

I want to hide some fields with conditions, for example, if the user choose ' No answer', some fields don't appear, I feel very lost in functions, since I'm a novice. Another thing, if the user types '2 'in the field ' number of children ', two fields will appear for each child's name and date of birth, how can I handle this action. I'll be very grateful.

Thank you very much.