App crash with GC When an object added to firebase - Android Studio

Hello i have an android app

when an update ( Insert new data in firebase or update an attribute ) done in firebase the app will crash for 15-30 sec .

when i checked log , it show that's in that time the GC is working and it's take a lot of time to done his work so the app crashed a lot of time and in the phone you can't do anything till GC finish there work , i don't have so much data in my database also my application is not that bigger .

You can see the log here :

I/lhindeliveryma: Background concurrent copying GC freed 325485(8953KB) AllocSpace objects, 0(0B) LOS objects, 36% free, 10MB/16MB, paused 218us total 136.046ms
W/Looper: Slow Looper main: Long Msg: seq=1424 plan=02:06:39.877  late=2ms wall=2060ms running=1848ms runnable=39ms io=29ms h=android.os.Handler c=com.google.firebase.database.core.view.EventRaiser$1
I/lhindeliveryma: Background concurrent copying GC freed 373886(10MB) AllocSpace objects, 0(0B) LOS objects, 35% free, 11MB/17MB, paused 259us total 155.904ms
I/lhindeliveryma: Background concurrent copying GC freed 501873(13MB) AllocSpace objects, 0(0B) LOS objects, 33% free, 11MB/17MB, paused 394us total 247.891ms
I/lhindeliveryma: Background young concurrent copying GC freed 323701(8831KB) AllocSpace objects, 0(0B) LOS objects, 31% free, 12MB/17MB, paused 537us total 116.240ms
I/lhindeliveryma: Background concurrent copying GC freed 567601(15MB) AllocSpace objects, 0(0B) LOS objects, 32% free, 12MB/18MB, paused 430us total 288.562ms
I/lhindeliveryma: Background young concurrent copying GC freed 351662(9586KB) AllocSpace objects, 0(0B) LOS objects, 32% free, 12MB/18MB, paused 528us total 125.947ms
W/Looper: Slow Looper main: Long Msg: seq=1425 plan=02:06:40.037  late=1902ms wall=1811ms running=1692ms runnable=2ms h=android.os.Handler c=com.google.firebase.database.core.view.EventRaiser$1
I/Choreographer: Skipped 180 frames!  The application may be doing too much work on its main thread.

here's what log is saying

and this is my code how i receive data from firebase :

        FirebaseAuth mAuth;
        mAuth = FirebaseAuth.getInstance();

        FirebaseUser user = mAuth.getCurrentUser();


        firebaseDatabase = FirebaseDatabase.getInstance();


        EndLoop:
        databaseReference = firebaseDatabase.getReference().child("Orders").child(City);
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {




                You = new ArrayList<>();
                Now = new ArrayList<>();


                postAd = new OrderAD();

                boolean stop = false;

                for (DataSnapshot postsnap : dataSnapshot.getChildren()) {
                    if(!stop)
                    for (DataSnapshot postsnap1 : postsnap.getChildren()) {
                        if(!stop)
                        for (DataSnapshot postsnap2 : postsnap1.getChildren()) {
                            if (!stop) {
                                Order post = postsnap2.getValue(Order.class);

                                if (!post.getStatus().equals("تم التوصيل") && !post.getStatus().equals("تم الغاء الطلب")) {




                                    if (post.getDeliveryUID().equals(user.getUid()))
                                        You.add(post);
                                    else {
                                        if (post.getDeliveryUID().equals("")) {
                                            Now.add(post);

                                        }

                                    }

                                    if (!Offers.contains(post.getKey())) {
                                        Offers.add(post.getKey());
                                        if (Done) {
                                            show_Notification(post);
                                            You.clear();
                                            Now.clear();
                                            stop = true;
                                            System.out.println("Hello");
                                            break;
                                        }
                                    }

                                }

                                break;


                            }
                        }

                    }
                }

                if(!Done){
                    Done = true;
                }



                Collections.sort(Now);
                Collections.sort(You);


                postAd = new OrderAD(Offers.this, Now);
                recyclerView.setAdapter(postAd);








            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });

any suggestion to solve this ?