How should you respond to jokes made by colleagues?

Now that we know that the female colleague is joking, it is not difficult to answer. I can say to the first one, "You made a good joke. I'll buy a notebook right away. " Because the word "joke" in front of her is so childish that she doesn't take it seriously at all. For the second one, you can say, "Your jokes are very good. I will definitely bring you two meals next time. " (It's not indecent to say so. )