Below are two paragraphs of text that have taken from the website of a Beijing-based Chinese-English translation service. Although the English is easy to understand, it contains several mistakes. This tells you that the text was translated from Chinese to English by someone whose first language is not English. It is another illustration of the need to use as a translator someone whose first language is the target language, the language into which you are translating the text. Alternatively, the translated text should be submitted to an editing service, such as that provided by English Writing Services, to review and correct, if necessary.
The mistakes are underlined in the text below. The explanations follow the two paragraphs.
As a local Chinese translation company registered in Beijing, China, we have been providing professional Chinese translation services to clients from various industries throughout the world. Thanks to our quality and consistency, we were able to maintain long-standing relationships with a great majority of these demanding customers, who, after some testings and comparations, have eventually decided to designate us as one of their few top-tier vendors.
All the source files entrusted to our company are translated by highly qualified Chinese translators, and then proof read by seperate linguists. Our professional English / Chinese translation team has proven experiences in various industries with all kinds of documents.
were - "have been" is a better choice.
testings - "testing" should be singular. "Evaluation" is also suitable.
comparations - "comparisons" is the correct word
proof read - "proofread" is the common spelling.
seperate - "separate" is the correct spelling.