A bilingual speaker in a workplace can never do such a good interpreting job as a trained interpreter, even when he or she has been asked to help out when a monolingual person appears on the scene who cannot speak the workplace’s language. Misunderstandings can easily take place if a trained interpreter is not at hand to do the job.
Most “bilingual” individuals are able to speak and be understood in two languages. However, there is more to interpreting and translation than bilingual abilities. Interpreters don’t have the time to ask for clarification when interpreting. They have to have a complete and thorough understanding and be able to fluently translate accurately and quickly the information or conversation put in front of them without help or consulting with experts. They can’t afford to pause and contemplate a suitable translation, for example at a court hearing, as leading parts of the ensuing conversation might be missed.
Additionally, no professional interpreter will ask for any repetition so that he or she can get the translation correct.
There is more to professional interpreting than the interpreter just working with the two languages he or she is competent to translate. There is the language related to the interpreting situation that is important too. For example, an interpreter working in a courtroom has to understand legal language, while an interpreter working in a hospital environment has to be conversant with medical terminology. If an interpreter has been called in to interpret in a taxation dispute, the language of taxation has to be known well. Someone who is just bilingual will have unlikely spent time learning the specialist language of the court, medical and taxation contexts.
A professional German translator or interpreter may have a complete understanding of at least two languages, but there is more to language than word for word translation. Language is influenced by the culture it is spoken in so native speakers use idioms and nicknames which convey meaning beyond the word for word translations. An interpreter can use the terminology that matches the person he or she is interpreting for.
Bilingualism can help to provide a foundation for a career as an interpreter, but a true interpreter has a far more thorough understanding of the language and its nuances.