How can I make a wifi connection to my drone (with my phone), if eg. the remote suddenly goes down or breaks (the spark is in the air) What possibilities do I have to control the drone ? Becausce I don´t have a wifi connection with the smarthphone to the drone, only between the RC and the phone.

You can't!
But the auto RTH function will kick in after 3 seconds of no RC-AC connection. Usually

Hi, sir. I would recommend you fly with DJI GO 4. Or it will not have the flight record. Also, it will be safer if you can view all the info about drone in the app. Thanks for your support.