"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean—neither more nor less."
from Lewis Carroll´s "Alice in Wonderland"
Translating and interpreting is about so much more than being bilingual. Fluency in your working languages is a prerequisite, of course, but what distinguishes a professional translator and/or interpreter from a bilingual is extensive training.
A professional translator and interpreter is a language expert, alive to the nuances and power of words, someone who has spent years studying in order to be able to interpret context and culture.
If you have spent time and effort creating the perfect text or speech, you want that attention to detail to be echoed in its translation.
That is something that you will only receive from a qualified language professional.