I've been reading about archaeology and the city of Ai and that Joshua's conquest could not have happened there as the Bible claims. I really could use some help with that.
You need to keep in mind that the "datings" by archeologists are based on modern-day chronologies which have a likelihood of errors. What is interesting is that there is no dispute about the fact that Jericho was destroyed and in a manner consistent with what is recorded in the Bible. What has been recently argued is that the time frame is wrong. This is usually argued from Egyptian chronology, but I know of at least one Egyptologist, David Rohl, who has some very solid evidence that modern Egyptian chronology is off because it doesn't take into account that some dynasties in Egypt overlapped. See A New Chronology under the topic of Joshua.
The sad thing is that when conflicting evidence is found, a lot of people tend to go with the ones contrary to the Bible simply because they are different. It is only when they are dragged kicking and screaming to the conclusion that the Bible is right, do they acquiesce and then run to find something else that contradicts the Bible.