IOS App Getting slow

Hello Everyone! I hope you all are having a wonderful day. I am wondering if some can please help me. I am using firestore. In my app, users can publish elements, delete, and modify them later. When the user open the app, the UserManager fires a registration listener that fetch all the elements from the database. On the listener, i am focusing on elements that was added, modified, and deleted. Each time i receive a response from the database, the usermanager update the users property which is an array.
But how do I update it? I will send the code so you can see how i do so. After the update has been made. The users property of the userManager has a property observer that call a delegate method.
My MapviewController conforms to the delegate protocol, Each time the mapviewcontroller, receives the update, it call a function that update the user interface. The code does what i want it to do. BUT, as soon as, i post more thant 5 elements, the User interface takes to much time to update. I guess that the problem is with the function that update the users property. If someone wants to help me, please let me know, i will post the codes, so you can have a complete view of it.