onesignal notification open in phone web browser instead of app

Question

HI every one first of all i am not a programmer but i really need help i made an app for my wordpress blog using template web2app installed onesignal plugin in my wordpress and automaticly send notification across platforms but when it send the notification to the app and i press on it it open the link in mobile default browser instead of opening it in my app i contacted onesignal but they gave me this link to follow but i dont know how to do it https://documentation.onesignal.com/docs/links here is a copy of onesignal .jave

package com.sherdle.webtoapp;

import android.content.Intent;
import android.net.Uri;
import androidx.multidex.MultiDexApplication;
import android.text.TextUtils;
import android.util.Log;

import com.google.android.gms.ads.MobileAds;
import com.google.android.gms.ads.initialization.InitializationStatus;
import com.google.android.gms.ads.initialization.OnInitializationCompleteListener;
import com.google.firebase.analytics.FirebaseAnalytics;
import com.onesignal.OSNotificationOpenResult;
import com.onesignal.OneSignal;
import com.sherdle.webtoapp.activity.MainActivity;

import org.json.JSONObject;

public class App extends MultiDexApplication {

    private String push_url = null;
    private FirebaseAnalytics mFirebaseAnalytics;

    @Override public void onCreate() {
        super.onCreate();

        if (Config.ANALYTICS_ID.length() > 0) {
            mFirebaseAnalytics = FirebaseAnalytics.getInstance(this);
        }

        //OneSignal Push
        if (!TextUtils.isEmpty(getString(R.string.onesignal_app_id)))
            OneSignal.init(this, "REMOTE", getString(R.string.onesignal_app_id), new NotificationHandler());
    }

    // This fires when a notification is opened by tapping on it or one is received while the app is running.
    private class NotificationHandler implements OneSignal.NotificationOpenedHandler {
        // This fires when a notification is opened by tapping on it.
        @Override
        public void notificationOpened(OSNotificationOpenResult result) {
            try {
                JSONObject data = result.notification.payload.additionalData;

                String webViewUrl = (data != null) ? data.optString("url", null) : null;
                String browserUrl = result.notification.payload.launchURL;

                if (webViewUrl != null || browserUrl != null) {
                    if (browserUrl != null || result.notification.isAppInFocus) {
                        browserUrl = (browserUrl == null) ? webViewUrl : browserUrl;
                        Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(browserUrl));
                        startActivity(browserIntent);
                        Log.v("INFO", "Received notification while app was on foreground or url for browser");
                    } else {
                        push_url = webViewUrl;
                    }
                } else if (!result.notification.isAppInFocus) {
                    Intent mainIntent;
                    mainIntent = new Intent(App.this, MainActivity.class);
                    mainIntent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT | Intent.FLAG_ACTIVITY_NEW_TASK);
                    startActivity(mainIntent);
                }


            } catch (Throwable t) {
                t.printStackTrace();
            }
        }

    }

    public synchronized String getPushUrl(){
        String url = push_url;
        push_url = null;
        return url;
    }

    public synchronized void setPushUrl(String url){
        this.push_url = url;
    }
}