Translation:The diseases take a long course.
Absolutely. Duolingo (once again) simply has it wrong. The correct phrase in English is "The diseases take a long time to run their course". While the meaning given by the app "can be understood" its lexically and semantically wrong. To "take a long course" is an expression that would never be used without an appropriate predicate in English. The app fails its users yet again.
One would not normally say "the diseases take a long course" in English, but it's understandable. I would usually say "the disease/illness lasts a long time." It is not uncommon, though, to hear "we have to let the disease run its course," meaning we have to wait for the illness to go away on its own.
And that would be the point. Many commenters have thought that the disease was just going to take a while, whereas you are suggesting the treatment, not the disease, is what will take a while. Your suggestion makes as much sense as the other, because you have to add information to make this an English sentence, information that is not present in the German. So, too, the other option. And that is why this translation should be corrected by a native English speaker--it does not make sense in English. Reporting.
Nah, "takes a long progression" is even worse. I don't think one can "take" a progression. It doesn't sound right. These options would sound better:
- The disease progresses slowly
- the disease progresses over a long period of time
- progression of the disease is slow
- progression of the disease happens over a long period of time
Verlauf can mean process, but in this case, course is the correct term in idiomatic English when discussing the length of an illness. Process does not really have any meaning within that context. This is the problem with translation exercises when learning a new language: the software will flag your answer as incorrect based on idiomatic use of both languages.
In English, this might mean: 1. There is a long incubation period (before you notice you have contracted the illness). I was fine on the flight and for several days after returning home, but I had been in contact with someone infected. 2. It is likely to take a long time before it is cured. 3. It may take a long course of treatment to solve the problem.