I want to write a book the problem is i dont know what to write about and were to get started ANY SUGGESTIONS?

Ok here is the thing i really want to write a really good book that people would love to read but the thing is I don't know what to write about or how to get started... I am 13 years old and love to read and write I just thought how wonderful would it be to read a book that i personally write and then published it but then i really cant find a good topic that i can really get started with and i would just love it if you guys could all help me figure out what to do (: thanks for taking your time and helping me out :)