An important aspect of a good translation is the four-eyes principle: the finished translation is proofread by another person, preferably a native speaker. This ensures that nothing is overlooked, no transposed digits or similar things have crept in, and any other errors are found and corrected. After all, translators are only human and make mistakes every now and then.
The same principle applies to texts that you have written in a different language – they, too should be proofread by a native speaker (editor), in order to find and smooth out any linguistic deficiencies, grammatical inconsistencies, etc. so that the end result is well-rounded.
I am available as proofreader and editor for English and German of both translated and original texts (for example degree dissertations, term papers, correspondence, applications, etc.) and check them for grammar, spelling, linguistic flow and style, among others.