How to turn on sound in iPhone XR?

Question

iPhone

There is no sound in applications, games, sometimes the sound disappears when making calls.
There are no physical problems. I looked in the settings, but there is no such thing.
At the same time, when I turn on any melody in the ringtone selection settings, it is there and I make it quieter (so as not to go deaf), and there the volume control and the red crossed out bell are displayed above. I don't know how to make it not crossed out. Please help me figure out these details.

Answer 1

red bell is silent mode.
https://support.apple.com/en-us/HT208353