CATCHING UP AFTER FALLING BEHIND.
I am trying to regain my level in German but I seem to be losing the battle. I cannot understand why some topics need many more lessons to be redone to complete the topic, even though the errors and time lapse are less than for other lessons ?
Your stats ( https://www.duolingo.eu/skeelesirma ) say that you do 32 XP per day on average. When returning to Duolingo after a long time, 3 strengthen exercises (30 XP) are often not enought to regold even one single skill. In other words... if you want to see your tree golden, it's going to be a hard work for sure. The question is if you need it. Maybe just pick specific skills you remember being problematic in the past and repeat the exercises in them. If I ever return to my German tree, this will be the strategy for me.
About a year ago, when I had only nine skills left to do to complete the German tree, I decided I would, each day, regild two of the already completed skills before finishing the last nine. It didn't work. The new skills remained untouched, so I finally decided recently to continue regilding two old skills each day, plus one exercise in the new skills. It's a slow slog, but I keep progressing. I wouldn't worry too much about the speed at which you're regaining your level. As long as you're making mistakes, and figuring out why, you're learning. Keep it up.