How do you know Hamlet is being serious? You should be more careful with him,
How am I supposed to know?
Dad he's always so nice to me. He even gave me this promise ring!
That means nothing. He can say and do whatever he wants, but he could change his mind anytime. I think you should spend a lot less time with him.
I'm serious, Ophelia. You would feel silly if you wasted your time on something so pointless. Come on, Ophelia. Please.
Polonius is asking Ophelia about her relationship with Hamlet. Ophelia doesn't know exactly what Hamlet's intentions are, but says he is being really sweet lately and is fun to hang out with.
Ophelia argues that Hamlet is very nice and even got her a promise ring. Polonius doesn't buy it and tells her she needs to spend less time with him because he could be only keeping her around to play with until he gets bored with her. Ophelia is upset at Polonius and tries to argue again.
Polonius continues to tell Ophelia she needs to be careful with Hamlet. He tells her she would feel silly if she wasted so much time on something so pointless. She is upset, but unwillingly complies.