How do I fix lagging and app crashes on my new iPhone 15?

I have recently purchased an iphone 15 128 gb from amazon

and from the very 1st day my phone was lagging like anything i cant click 2 or more photo, like recently i was clicking picture suddenly camera stopped working and black screen, not only camera but there are some other apps where i am facing same problem

#iphone15 #applesupport

[Re-Titled by Moderator]