A good translation does not show its nature
Apart from a correct transfer of content and the absence of grammar and spelling mistakes, a good translation does not let the reader become aware of the fact, that he or she is reading a translated text.
A translated text needs to read like one, that was originally written in the target language. One of the biggest challenges in this respect is to not (slightly) adopt the source language’s sentence structure. That is why, among other factors, quality-conscious translators only translate from their foreign language(s) into their mother tongue and not vice versa.