How to quickly create an application (social network) for Android?

Question

Mobile development

Hello. Started learning Java and AndroidStudio about 6 months ago. I already have a normal understanding of Java. And I know how to do something in AndroidStudio.
I want to make my application in the format of a social network. Are there ready-made solutions that can be quickly assembled and do not require deep knowledge?
The application will be in the style of VK for mobile.
I mean, why create your own chat if there are already hundreds of them written. Or activation with registration and authorization, or uploading and displaying a photo. Where can I get these pieces of ready-made activities and combine them in my application?
Maybe somewhere there are ready-made open source social networking applications that you can remake for yourself, I haven’t found anything on the Internet yet.
I would also be very grateful for useful links and advice on how best to do this.