hard reset does not work

I am not sure what you mean by hard reset, however  Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:

• Press and quickly release Volume UP button
• Press and quickly release Volume DOWN button
• Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF). 

Axel F.

If Force Restart does not work then - Follow the instructions in this article by Apple ➔ If your iPhone is Non-Responsive or Frozen and see if that helps.

Axel F.

Get live expert assistance by contacting Customer Support by phone or chat:

• Call Apple Support at 1-800-APLCARE. 📞
• International Support. 🌐
• Contact Apple Support. 📝
• Live chat using Messages. 💬