You have now conquered your shiny Polish golden owl. Yay!Now it's time to advance to the next tree level and probably discover more content and harder lessons with each level.
You didn't do enough Polish lessons recently but you still have to finish 100 more sessions to get all of your skills to Level 5 — check back here when you practice a few more lessons to see how soon you're supposed to level-up your Polish tree. The longer you practice, the more accurate is the prediction.
Keep going! =)