How can i submit a coding challenge?

Answer 1

Daniel, if you are talking about the challenge quizzes for play section then you can make that via going in quiz factory.
To access quiz factory go to the main activity page and tap on top right three vertical dots and select quiz factory. Then in the quiz factory tap on "suggest quiz" and submit your quiz and wait for the reply came by sololearn in form of approval or decline of quizzes.
And if you talking about coding assignment then you can make that via going on lesson factory. You can access lesson factory same as quiz factory just select the lesson factory and suggest lesson type with assignments and submit it.

Answer 2

I also don't know
actually sometime I wanna join T_T :(

Answer 3

thank you @Gawen

Answer 4

How long have you been on sololearning