I have problem in samsung A15 features. Even samsung members not working properly. What's the problem?

How to check thatapps are working in background and drained battery? How to stop them? Plz guide.

Assalamu AlaikumCan anyone tell me about theft protection lock. It is shown on samsung A15 screen after calling but it's icon doesn't show on top of the screen. It's only shows as theft protection lock in faint look on screen. Why it is happened?

Despite of super fast charging it is slow charging. And now it doesn't charge.please guide .

Please tell me what's issue with sim cards having no service Galaxy A15