Take a look this post - it’s a log I kept when I did Spanish course 1 a few weeks ago.
To summarise - I felt as though I was stuck, that I was not remembering anything. But I pushed on, 1 lesson a day and then graded myself on the last lesson, to be pleasantly surprised that I could remember some of it.
Some lessons were straightforward, other lessons were complete mysteries to me. There were times when I finished a lesson and I felt as though all I’d done was say blah, blah, blah for half of it.
I completed the last lesson and felt disheartened that I only did 22% of it correctly, until @aran pointed out that I had done 60% of it sort of correctly. 60% is enough for me to be understood in Spanish.
If I redid 3 Spanish lessons I struggled with badly (15, 16, and 17) I think I would feel as though I was stuck as well. I would get half of it right, but be blank on the other half.
So I’ve not bothered. I’ve simply gone on with course 2. If I can remember 60% of course 2, then together with the 60% of course 1 I’ll know a lot of Spanish. I’ll worry about the bits I’ve not remembered in the future.