Cannot keep a tree gold
I finished my tree a few days ago, now it is impossible to keep it gold. around 20 lessons keep changing a day, till the point none of my tree is gold anymore.
I can do around 10 exercises a day, but after I finish them half is not gold anymore, and this get frustrating. if I decide to do even more, than after I finish the next day they are all back to practice.
can this be stopped? I mean I want to put back in gold my tree, then I can continue practicing in a pace I can follow.
The more times you redo a lesson, the longer it will stay gold. This takes a while to build up, but eventually you'll hardly have to practice at all to maintain a gold tree. If it's making you feel overwhelmed, try redoing just a few a day. (I strengthened three skills a day every day for...I'm not sure how long.) You won't regild everything at once, and that's fine; sometimes--especially at first--things will degild and you'll feel like you're getting further behind, but just ignore it and carry on doing your three a day, or whatever. Eventually the degilding will slow down, and you'll catch up. (Now I do one general strengthen on my Esperanto tree every day and that's plenty to keep it gold.)
As has been mentioned, this is just the result of finishing the tree very quickly. For instance if you finished 10 skills on the same day, you will be (expected to be anyways) practicing all 10 of those skills the next day.
As you continue to practice, the rate at which you will be practicing each practiced skill will go down.
To prevent this from happening on future trees, just slow your pace and be sure to be practicing the already completed skills before moving on to new skills.
You only have a 12 level, I think its normal what is happening to you, because probably you finished the tree like an icecream in a very hot day.
One thing that helps is re-gilding the tree from the bottom up. Occasionally you will get two strengthens for one exercise. Once, I even got three. As the weeks go by, your tree will get more and more gold, and it will take less exercises to maintain.
Since it appears that you finished the tree very quickly it will be very difficult for a while to keep anything gold. That degilding will slow down with time as you strengthen the lessons more. This degilding phenomenon is especially prominent in Esperanto, other languages do not degild as quickly. The last time this was pointed out it was suggested that this was due to the fact that Esperanto has so many subgroups in each lesson.