I am getting the following error:

TypeError: Cannot read properties of undefined (reading 'set').

I am trying to update the endTime in the script and i want to do it for each user then calculate the total amount of hours worked and update it in a field called 'totalTime'.

const {
        initializeApp,
        applicationDefault,
        cert,
    } = require("firebase-admin/app");
    const {
        getFirestore,
        Timestamp,
        FieldValue,
    } = require("firebase-admin/firestore");
    
    const firebaseConfig = {
    xxxxxx
    };
    
    const serviceAccount = require("./fitness-69af3-firebase-adminsdk-c3hmg-c7fda98049.json");
    
    initializeApp({
        credential: cert(serviceAccount),
    });
    const db = getFirestore();
    
    const age = "30";
    
    async function main() {
        const fitnessRef = db.collection("/food");
    
        const snapshot = await fitnessRef
            .where("role", "==", "junior")
            .where("age", "==", age)
            .get();
    
        if (snapshot.empty) {
            console.log("No matching documents.");
        }
    
        snapshot.forEach((doc) => {
            let doc1 = doc.data();
            let schedules = doc1.userInfo.schedule;
            console.log(schedules);
    
            const res = schedules.ref.set(
                {
                endTime: "17:30",
                startTime: "09:00",
                // totalTime: "{endTime - startTime}"
            },              { merge: true }
            );
        });
    }
    
main();