Men: How can a girl tell if an older guy is interested in her? He's 40 and Im 24 - do u think he likes me or just being friendly?

Im friends w one if his colleagues, & was going out to dinner to catch up w her, & then at the last min as we were walking over to the restaurant, I see him walking up to us, & she turns to me & says, "I hope u dont mind I invited [guy] because he REALLY likes u," & she turned around to look at my face as she said it. Another one of his friends who I was friends w before I knew they knew each other told me "u should go find [guy] while you're over there," because we were going to be in the same country briefly over the summer.

He hasnt made any really obvious moves, so I just want to kno what an obvious move would look like from a guy this much older than me-does it seem like he likes me? When we're alone, we have really deep convos, & he initiates asking me about my future life plan & goals, & does stuff like say "she's really smart," if I say something in a group convo.

Once, we were at dinner in a large group, & the group was all sharing their dating experiences, but someone made a joke that changed the subject & so I never got to talk about my own dating habits, but when everyone was leaving the dinner party, I saw him lean over & whisper something to his same female colleague who I'm friends with. At first, bc he was looking at me while whispering, but then I thought its just a coincidence - sometimes ppl just have to put their eyes somewhere, so I dismissed it, but as I was leaving, this colleague held me back & said "I've never asked you but are you seeing anyone?"