The structure of the course
I understand that it must be so in the beginning, but as I get towards the end of the course it feels more and more like a problem that there are skills like "Verbs Conditional" and so. That means that after a couple of answers in a lesson you know what the pattern for that entire lesson will be, and can answer without thinking about it.
It would be much more useful if there were lessons like "Jumping, running, flying" and that would contain questions in a mixture of tenses.
And, as a complement to this, please make sure to stop first asking for a translation of a sentence from one language to another and then immediately after that, the translation of the exact same sentence in the other direction. I just had that exact answer read out loud to me. It's not much of an exercise to write it down again.
I'm not saying that the same sentence can't be translated in both directions in the same lesson. But please don't allow them immediately after each other!
I think you are right, but Duo seems to find the best effect in permanent repetition. That's the reason for the golden/not golden skills. It seems to be more important to repeat more often than smart