Jitsi-meet: Could not find method android() for arguments on project : react-native-background-timer

Hello,
I’m following this https://github.com/jitsi/jitsi-meet for jitsi-meet android app. i have installed npm and nodejs. when i tried to run that code on android studio i got following error

could not find method android() for arguments on project : react-native-background-timer of type org.gradle.api.Project

I have addes package.json file into node_modules as previously i got package.json missing error.

how could I resolve this??