Thanks for your questions.
Historical and Scientific challenges to the Bible are issues that many people struggle with. And while many apparent inconsistencies can be explained through careful investigation, there will always be things that puzzle us and can’t be explained. When there are apparent inconsistencies between the bible and science, the Christian’s stance toward the Bible is to trust what God has told us and recognise that we may not have the whole picture.
One of the things to remember is that the Bible does not pretend to be a scientific textbook. It was not written to answer our scientific questions rather it was written to introduce us to the God who created us. Remember that science can tell us how something works or came into being but it cannot tell us why it happened or what its meaning or purpose is. The Bible, on the other hand, may not tell us how but it does tell us why things are the way they are and what they mean. So to question the bible from a scientific perspective will always come up with issues.
I start with this because the questions your friends are raising are good ones and ones that I’m not sure there are definitive answers for. But here are some thoughts that might help.
Adam living to 930 years old does seem odd. What is interesting is the way that the Bible tells us these amazing details without trying to explain or justify them. This could tell us that for the author these details were not unusual at all. He was simply writing what happened. So you could try admitting to your friends that it seems strange to us, but not to the author.
What is also interesting is that after the Flood (Genesis chapter 6 to chapter 8) something seems to have happened to bring the ages of people back to more of what we would expect. By the time we get to Genesis chapter 11 and verse 32, we learn that Terah lived for 205 years (which is still a long time, but less than 930 years!). Further on in the Bible it seems the average age was about 70 years (see Psalm 90:10). So it seems that something happened to bring the ages to a level that we would accept as normal. I’m not sure anyone really knows why this happened. All we can say from the Bible is that something did happen.
Regarding the origin of races, I’m not an expert on the science of which race came first. The Bible’s take on your question is that Adam was the first man (it doesn’t say what race he was because at that stage there were no races; just one man). Eventually, as humanity multiplied people spread out over the whole earth and nations were formed. What we now call Africa was no doubt included in this (Egypt is certainly mentioned early in the Bible - Genesis 12 verse 10).
Very briefly, two comments regarding answering your friends when questions become slightly aggressive. First, I would be very surprised if there was any question that had not been asked (and answered in some way) by others before. Yet no question has meant that Christianity has come tumbling down. So you can chat with your friends with confidence because you know that their question isn’t going to defeat Christianity. Second, ask God to help your friends understand.
If they are becoming aggressive, I would challenge them to read the bible for themselves because I believe you will find that they never have and that they are speaking about things they have heard other people say. Maybe you could encourage them to read it with you.
There is much more that could be said but I hope this is helpful.