Fun is used to describe something that you enjoy doing.
It is fun to play football
I have fun when I learn English
I have lots of plans for the weekend, it is going to be fun
Something that you like to do, something that makes you smile is fun.
Funny is normally used to talk about things that make you laugh.
This movie is very funny, I haven’t stopped laughing
I always laugh at funny jokes
I like going out with Paul, he is very funny
Try to remember the rule like this;
I really like to watch football, I have fun watching football. I enjoy watching football. I don’t normally laugh watching football, football isn’t normally funny.