"I never know how to finish my text."
Translation:Eu nunca sei como terminar meu texto.
Is "Eu nunca sei como terminar o meu texto." wrong? I thought the article was optional except in cases like after prepositions (where it's required) and (singular) family members (where it's prohibited - or is that just Italian?). If this is wrong, can someone explain why?
I can't find any reason why it should be considered wrong, and I always add the article myself. By singular family members you mean nouns like husband? As far as I know, "O meu marido" isn't prohibited. Anyway, you should probably report it as correct the next time you see it.
"Eu nunca sei terminar meu texto" is wrong? What about saber + infinitive =to know how to do something?
Isn't wrong, but is a little strange! I didn't understand the second question.
I wrote "Eu jamais sei como terminar meu texto" and was marked wrong. Is "jamais" used in a different way than "nunca"?
'Jamais' is Hardly used in Brasil. And depending the context it can mean something like 'a distant moment' or a 'probably moment'. But may mean exactly the phrase of the exercise, so you can report if happens again!