It's pretty easy actually.
I appreciate the fact that you want to make something similar to sololearn so lets look how.
So sololearn is available on android, ios as well as web that means to make the User interface Or the front end you are gonna write code in Java, swift as well as Web Stack of html css js, etc. by yourself. Now I don't think that you have a team of 50 people to make it.
So that was just user interface. Now from where do you bring the data. You also need a Backend to serve the content.
Wait what's your content from where will you bring the content.?
Okay let's assume you succeed in copying every functionality but there's something called value. The users and emotions that binds sololearn to its fellow sololearners is something you can never ever copy with just writing code.
So I guess that explains it all.
Hello Bhaskar Tiwari
Your curiosity as a beginner is admirable.. after all, we aren't proper human beings if we don't have questions 😂
However, as you can see, there are two ways of making something like Sololearn:
1. (The quick and easy way) Copy or make something similar seeing the Sololearn source code
2.(The beneficial good way) Get skilled in coding by learning and practice and get the solution out of your own head to make something EVEN BETTER
Which one you'll choose is up to you 🙃
Best of luck
Hey bro, if I am not wrong, you are new to the programming world, aren't you?
I have a suggestion for you not to wasting your valuable time in this type thinkings. Focus on learning.
Hope it changes your mindset.