Prayer Times App for Muslims

Hi all,
I want to make a prayer time app for Muslims. Are you using that kind of app or program?

• What is your favorite and least favorite feature if you already use one?
• What would be the first feature you expect from such an application?
• There are too many advertisements in the programs in the market, and it seems confusing to me to use them, do you have similar experiences?
• Apart from that, I am open to any suggestions and cooperation.