How do I turn my ringer back on my iPhone?

Check the side switch

https://support.apple.com/en-us/HT208353

How do I turn the ringer back on my iPhone?

I need to unmute the ringer on my iPhone X. Don’t know how I muted it and don’t know how to unmute it.

I can not hear the Ring on my incoming calls. How do I increase the volume of the ringer?