How can I set it on my cell phone so that when I'm on the phone and someone who is calling me, I can recognize and accept it?

Please give an easy explanation.

The function is called call waiting.

https://handyhilfe.swisscom.ch/huawei/p10/einstellungen-nutzung/schalten-sie-anklopfen-ein-oder-aus/

You have to activate the "call waiting" in the cell phone menu. However, this is only supported by all term contracts, but unfortunately this is not possible with many prepaid cards.