Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
First it is important to be aware that since you just met this person, there is no way to know objectively about him, his honesty, maturity level, integrity and more, but you have the advantage of having your friend who knows him, and that could be the best source you could have right now, depending on how well your friend happens to know him.
Now, even when your fiend could know about his and that help you in this situation, the only way to truly know how assertive and real this person is would be through direct sharing and time. It could be concerning the fact that after the first date he got this quiet, instead of showing more excitement, so that is something to take into account here. On he other hand he is telling you he prefers to work on building a friendship so you could know each other better and see how things evolve from there. This could be taken as a positive or negative strategy. If he is not truly that interested, he could use this plan as a excuse to justify his avoidance, passivity and real feelings. But many people could do this is they happen to be more introverted, cautious or reluctant to get close too fast because of personality and/or past experiences.
This is why I confirm that the only way to know is with time by direct sharing, where you take initiatives, hoping he does the same, without pushing anything, but building this friendship based on honesty, openness and respect. You would know how you feel through this process, share about it with him, and see how well it works for each of you.
I do use to suggest people to focus on building mature friendships first, in order to truly know each other instead of replacing reality with hopes, needs and expectations that could not math reality. Then if this person is truly honest, you would see more from his actions rather than from his words how much he really likes you and wants to share more and at what levels, and how you feel with him, and if you are comfortable with this process, what adjustments to implement and see how far you get.
You would see how worthy it is to work on it and be truthful with yourself, reminding that a good friendship or relationship require full reciprocity for them to work.
Does it make sense?