Why my device is not booting up

@aish49185 I just wonder if your phone is turning on but you may have a broken screen from the fall. You did not tell us if your Xiaomi vibrates when you turn it on and if you can still see it when you plug it into your computer. IF so, then it is most likely a display issue. If not, you will still have to take it appear to check for any torn or disconnected ribbon cables etc.

Since iFixit does yet have a guide for this, you can use something like this video Replacement displays are readily available at plenty of online sites. Find a seller in your geographic area so it will be easier if there are issues with the parts.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.