I want to ask several seniors (brothers) questions through QQ, and I have only met once, which is also an exchange, because I will work together in the future.

Explain who you are first, and your purpose is sincere and modest. Ask with an open mind and thank them after asking. Tell them there are other questions to consult in the future. If you have time, talk to them about other topics they are interested in, or professional knowledge. Remember to be polite anyway, but don't go too far and don't be too fake. Just show your true side. I hope it helps you.