For a competent translator (into his own language) it is always and only his own language that presents the real problems. I use the dictionary to remind myself of the possible words in my own language. I do not consider people have any business to be translating if they have to use a dictionary more than very occasionally in order to understand.
I do not use the dictionary to find out what the foreign words mean. The only times I use a 'foreign-to-own' dictionary a lot are when I am doing translation work.
The grounds for it were that when one uses an 'own-to-foreign' dictionary, the chances are that one will not know how to use the foreign words one finds." In other words, it was all right to use dictionaries from the foreign language into one's own, but not dictionaries the other way round. When I first became interested in foreign languages I often heard people say that it is perfectly all right for English-speakers to use French-English dictionaries as much as they like, but that they should be very wary of using English-French dictionaries. The result is that not only are many of the examples quoted in the dictionary completely untypical of the real everyday use of the words, which is mainly found in speech they have also been taken out of their broader context in newspaper articles, novels etc., which makes it even harder for the dictionary user to understand how the words are used. (A well-known example is the Cobuild English dictionary.) These computer collections are almost entirely of sentences and phrases found in written texts. "However you should beware of monolingual dictionaries that claim to be the latest in scientific lexicography because they are based on a huge 'corpus' of millions of words scanned by computer. One thing I find objectionable is the frequent use of "never". I suppose I'm doing this because his ideas reflect very much my own. The excerpts were edited by the author Amorey Gethin. The book is worth checking out (available on Amazon). Some excerpts from "The Art and Science of Learning Languages" by Amorey Gethin (AG) and Erik V.