It takes how many days to complete your first course??

Answer 1

It depands on your learning time and interest.
https://www.sololearn.com/Discuss/2332725/?ref=app

Answer 2

[Mine took quite a long time to finished]

There is no completion duration in SL's courses.

Depends upon you, you can even finish them in couple of hours, but not recommended "the aim should be to learn rather than finishing"