Indian American thinking about Islam and marriage after my best friend's request

As-salamu alaykum. I'm trying to make sense of how I feel after my best friend told me something big. We've been close for eight years and we're both 19. On Monday he said he wants to be in a relationship with me. I care about him a lot, and I'm not automatically against it, but some conditions he mentioned need serious thought. He asked that I embrace Islam if we were to be together. I'm genuinely curious and want to learn more, but converting is a major life choice. It would affect my family, my future plans, and my sense of identity. I'm not sure yet whether I'd accept Islam from personal conviction or mainly for the relationship, and that difference matters a lot to me. He also said that in the future he intends to have up to three wives. He was open and honest about it, which I appreciate, but I need to think practically about what that would mean. I've never considered being part of a polygamous marriage and I don't know how comfortable I'd be sharing a spouse or what my role would look like. I need to figure out my boundaries and whether they match the life he imagines. I don't want to dismiss the idea without understanding it. I need to learn more about his beliefs, how commonly this is practiced or expected in his community, and what the real-life responsibilities and emotional realities are. I also need time to reflect on my own faith journey and whether converting would be true for me or only for him. Any advice on approaching this respectfully, learning about Islam sincerely, and talking through expectations with him would be really helpful. JazakAllah khair.