How to use WIFI and SIM data at the same time

HOW TO USE WIFI AND SIM DATA AT THE  SAME TIME .

why do I want to this?

1.Well you might be browsing with your SIM networks data and you might want to join a group created on Xender to receive an app,  but joining the group requires you switch on your WIFI and switching on your WIFI automatically  disables your SIM network data.

2. You might have limited data on your WIFI source, and you are downloading and would wish to continue the download on your SIM network data without pausing the download.

HOW DO I GET THIS DONE.
 
well this trick is limited to phones using andriod 6.0 and above
.
1. Goto settings

2. OpenDeveloper options

3. Scroll to networking

4. Select and enable cellular data always active

NO DEVELOPER OPTION IN SETTINGS? 

GOTO ABOUT PHONES,  TAP BUILD NUMBER  UNTIL DEVELOPERS OPTION IS ENABLED