(1) -Hey. What are you going to do on Sunday morning?
(2) - Hi, I don't know yet.
(1) - Have you ever been to the planetarium?
(2) - No, I've never been there.
(1) - Len's go then. It's worth seeing.
(2) - Why not! See you tomorrow morning then.
P.s. Hey и Hi (приветствия), если не нужны, можешь убрать.