I will not fail this time. it is not a literal translation but express the same idea. it should be accepted, right?
It is a similar ideia, but the best translation for 'errar' is 'to miss' or 'to be wrong'. The best translation to 'fail' is 'falhar'.
I said "I will not make mistakes..." and it was marked wrong because I should have said "make a mistake". What I want to know is why errar, literally "to err" has to refer to just one mistake. A piano student might make any number of mistakes in a recital, but it's still errar, isn't it? And in the next recital he promises his mom he won't make any mistakes this time.
I do not know a grammar rule to set on this example. But we actually say desta/dessa.
I will not go wrong this time - should also be accepted. No natural English speaker would say - I will not err - it's too formal