You should be able to understand the majority of texts without the aid of a dictionary, to the standard of an educated native-speaker. You do not have to be able to write to the same standard (particularly in terms of grammar, which few non-natives will ever fully master), but you should be able to understand concepts as well as any native. A good translator will use a dictionary and other resources to find the precise words to express the concepts, terms and ideas in the target language, but should also remember that such tools are there to assist only, and cannot do the work for them.