Hello Naoya Kojima, 
I think you have not completed end to end see total video may be missing from your end one of the video (try to begin with start again may be you will got success this time)

Thanks and Regards,
Akshay Deshpande

Hi Naoya,

You must be missing some video, quiz or excercise. I did not face such issue for any section yet. Outsystem have changed their platform and mark it done once you actually complete it, "Next Lesson" may not mark it done. 

You should check excercises, it may not marked done, specially last one.

Best of luck.

Mr. Akshay Mr. Mohit

Thank you for your replaying.

Yes, I will try to watch videos with start again.

I understood how to progress the bar.

I move the mouse cursor over the "information mark" under the progress bar.

I did not stay the page untill each lesson's duration, so I did it.

Then this problem was solved.

Thank you everybody.