Okay kiddo, so a long time ago, there was an empire called the Ottoman Empire. They ruled over a lot of land in present-day Europe, Asia, and Africa. The Ottomans were very powerful and had lots of resources like soldiers and money.
But as time went on, the Ottoman Empire started to face some problems. One big problem was that other countries began to get stronger and more advanced. They had better technology and weapons, which made it harder for the Ottomans to compete.
Another problem was that the Ottomans weren't always nice to the people they were ruling over. They made some groups feel left out and angry, so they rebelled against the Ottomans.
And finally, the Ottoman Empire got involved in a lot of wars that drained their resources and weakened them even more. All of these problems added up over time and eventually the Ottoman Empire started to fall apart.
So, in summary, the Ottoman Empire declined because they faced tough competition from other countries, they weren't always kind to the people they ruled over, and they got involved in too many wars that drained their resources.