Welcome, @dicker123456 - and that’s a very good question. I must say, you’re starting off in the “deep end”, but it’s certainly a very interesting prophecy!
Daniel 9:1 says that this prophecy comes in the first year of Darius, the new Persian king since Babylon has now been conquered. So the Babylonian Captivity is ended, and the command to emancipate the Jews is imminent.
In Daniel 9:2, the prophet has been studying Jeremiah’s prediction of the 70 year captivity of Israel which has now been fulfilled. The reason for the 70 year captivity was because God had said that every seven years, the land was to “rest”, or lie fallow, for one year (Leviticus 25:2-5). But Israel had not observed this for 490 years, and so now God had deported the nation to Babylon to give the land back all of its lost sabbaths at once (II Chronicles 36:20-22) - in fulfillment of Leviticus 26:33-35.
As Daniel is considering this, God sends an angel to give him a prophecy about the next 490 years of Israel’s history down in verses 24-27. When the angel speaks to Daniel about so many weeks of this and that, the “weeks” he’s meaning are these seven year periods. These are “weeks” of years, not days.
And verse 25 says that the countdown will begin with the Persian commandment to restore and to build Jerusalem. And the length of time from that countdown until Messiah the Prince will be seven weeks, or 49 years, plus threescore and two weeks, or 434 more years - for a total of 69 weeks, which make 483 years.
He breaks this total up into two segments (7 weeks and 62) to describe what will happen in each.
During the 7 weeks, the street shall be built again, and the wall, even in troublous times, which you can read about in Ezra and Nehemiah as Jerusalem is rebuilt despite much enemy resistance.
Verse 26 says that after the 62 additional weeks, shall Messiah be cut off, but not for himself. That’s the crucifixion of Christ somewhere around 30 AD. I do not pinpoint it exactly since most historians believe that the BC/AD divide might have been miscalculated by a very few years - that is, Jesus might not have been born on Christmas Day in 1 AD - but that’s still really close.
Since the command for the Jews to return and rebuild came in 457 BC (Ezra 7:11-26), you can see that Daniel’s prophecy certainly put’s the Messiah’s death very much in the historical ballpark.
Now, I have seen some very detailed studies that have meticulously nailed it down to the day. But since they are far out of my league, I’ll just trust that God did fulfill it to the day even if I cannot explain it as well as some others.
But I hope this will help you with the gist of your question.