@Marymut: To begin with, please head to Settings > Sounds and Vibration > Sound Mode, and make sure this is set to 'Sound. Now, toggle on 'Vibrate While Ringing', and ensure you have a Ringtone and Vibration pattern assigned. Also, tap on 'Volume' and make sure the Ringtone slider is at a suitable level. I'd also suggest checking Settings > Notifications > Do Not Disturb to make sure that this option is toggled off, as well as Settings > Connections > Flight Mode. Let me know if this helps.
