Newbie client needs help & advise

Hello everybody, 

Thank you in advance for reading and helping, although I am not sure if this is the correct place I should post my question, if I am wrong, please move my question to the right folder.

Background
Recently I engaged a reputable (4.8 star and more than 30 reviews according to Clutch) agency from to develop an app for me. I am trying to develop a messaging app with multi device login such as browser & mobile (ios & android). The app I paid for has an offline database in the device as well as online database hosted in cloud. The messages are sent via JSON-rest API technology.

Problem 1)

After the app has been set up, i notice that the app loads on every page I click on. When I change from individual chat to group chat, the page would load. So I mentioned my unhappiness to the agency and now my app does not have the loading animation but it still does not appear instantly. However, if I turn my phone into airplane mode, the screens appear instantly while switches from page to page.

As mentioned by the agency, this is normal. But I felt that something is wrong here, please advise what methods are available so I can rebutt the agency that they are using backward technology?

Problem 2)
As there is a messaging feature in the app, it allows individual or group chat within the app. However, everytime I send a message, the loading animation would appear. The animation would usually appear for about 1 second. I have not seen any messaging app that loads on every message sent, so I believe I am being short changed here.

The agency told me this is the best they can do. In 2018, I believe there are no more messaging apps that load on every message sent. How can I tell the agency that they are short changing me?

My plan is to use this discussion thread to show the agency that I am being short changed, so it is fine if you are replying with programming jargon or languages. Do let me know if you have any questions and I will try my best to reply them here.

That indeed does sound like an app that isn’t doing it’s job. I would never use an app that has to load on every message sent.

hi newbi am have verry delicate situation