Use only native speakers for your translation
An authentic and professional translator will offer translations from a foreign language only into their native language. They will know the source language to a standard higher than degree level, and will know their native language perfectly. Anything else is amateurish and usually results in a poor or ridiculous final text.
British standards in translation are very high and translators should be members of a professional body: the Chartered Institute of Linguists or the Institute of Translation and Interpreting. Translation agencies should have similar corporate criteria and use only professional translators.
These standards are not always so rigorous in other countries and sometimes those who have merely learned some English at school or university are deemed suitable for translating into English. The results are rarely good.
One example of inadequate standards is Italy where the matter of poor translation into English at tourist venues has now become a political issue. For strong views and some laughs readers can enjoy the “Inglisc: Mèd Een Eetaly” blog. China is another country that seems to be a major source of bad English and online examples are endless.
Needless to say, Google Translate and other software, especially free software, cannot do the quality work of a professional human either. This point is wittily made by Translator Fails on YouTube.
To get a good final result, please use professionals only. It may cost more, but it will be well worth it. You avoid embarrassment, misunderstandings and wasting your money.