Handling user's off-topic input

Hello,
I am currently creating my first bot ever which is focused on Football Laws of the Game.
After studying some documentation and watching video tutorials I should be able to create chatbot which is capable of talking about football laws.

But my Q is what about user's off topic input?
Currently, I am using "Fallback interaction" - If no conditions are met in some interaction, then I am using "my universal one" whith responses like "Oh, sorrry, I don't understand.", etc.

Is there any way how to handle it better? I would like to have chatbot which is capable of something like having "small talk" with user. Please keep in mind I am total beginner :).

Thanks for your help!