How to develop apps like Whatsapp & Sololearn?

Question

Hello everyone!!
I want to ask, what should I learn to make apps like WhatsApp and also SoloLearn?

Answer 1

If you mean mobile software:

- Android: Java
- IOS: Swift, C, etc...

Web development: HTML, CSS, JS, etc...

Answer 2

for ios, learn swift.
for android, learn java

Answer 3

Reference: https://github.com/signalapp