Order of lessons
What is the order I should do the grammar lessons. I think there was an indicator in the previous version for the next recommended lesson.
There was indeed a lesson recommendation before, but it was not very clever. This was just the lesson which was the biggest "barrier" for you to continue. I.e., if you had to finish 2 skills to unlock the next skill, the first of them had 8 lessons and the second 4 lessons, the first would be marked as "recommended". If you did 5 lessons from the first skill, you'd have now 3 and 4 uncompleted lessons, respectively, and the "recommendation star" would move to the second skill.
That said, if you have a few unlocked skills at a time, work on whatever skill you like. Use common sense, too. If you have a skill on Present Perfect and a skill on Past Perfect, it is probably better to do Present Perfect first.