Can you make the app work on the background

Cause whenever I'm putting my phone away or anything like that the praying time alarm doesn't work

I thought I didn't hear it at first and than I was waiting for it and didn't work in time and than I thought I didn't allow the notification and when I checked it everything is fine notification are allowed in my phone and are turn on in the app and one time I check the app to look at the time of a prayer and it ringed so I'm guessing the notification work only when I open the app which is that didn't help me cause I can't be using this app and my phone all the time so i don't know if it possible or not but can you make this app work as a background app so whenever I'm not using my phone or I'm in another app it ring and notify me of the prayer time is in and if this is an already feature please tell me how to turn it on cause the whole purpose for me to download this app is for it to notify me when praying time is in so please email me back if you got my msg and tell me what should I do