Firebase Cloud Functions Emulator Issue

I am using React Native with Firebase Firestore & Cloud Functions. In oder to test those functions locally, I use the emulator suite.

    -Application folder    --node_modules etc.    --react native stuff etc.    --some firebase configs and firebase init for client use etc.    ---Cloud Functions Folder    ----lib    ----node_modules    ----src [using typescript]    ----other stuff in Cloud Functions Package    -- other stuff in React Native Application Package

firebase deploy --only functions would transpile the ts files from src to lib and those js files would be used in production servers. But if I use the emulator, I need to transpile the ts file manually. Than the first error occurred: a gRPC version mismatch (like NodeJs Error - Failed to load gRPC binary module because it was not installed for the current system Expected directory?). Rebuilding both node_module directories did not work. I had to delete the node_modules folder in the top level "Application Folder" and do npm install.

Now I am dealing with this error:

firebase emulators:start --only functions[…]⚠  FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been created - call Firebase App.initializeApp() (app/no-app).    at app (/Users/user/Developer/folder/code/folderapp/node_modules/@firebase/app/dist/index.node.cjs.js:355:33)[…]

Does anyone know how to solve this issue?