"In the first line there are some words that I don't know." should be right as well.

So כמה מילים = several words? I'd only learned it with the meaning 'how many'.

Can יש be moved to the beginning of the sentence? Can בשורה הראשונה be moved to the end?

One of these annoying sentences at which one gets stuck, because there are many correct ways of translating it, but only a few are accepted by the app...

I believe this is an incorrect translation. If the Hebrew sentence began "לשורה הראשונה" then it would be correct to say "The first line has". Since it is "בשורה הראשונה" then the correct translation would be "in the first line their are". DL accepted that, but appears to prefer "has" to "there are".