Whether you are a translator, or simply reading a book in a foreign language, or your own (!), dictionaries are a vital part of your equipment.
In a sense they are the most boring part of one's library, and there is a temptation to throw them all away, and rely on online ones. But beware. If you want to look up older words, words that were current some decades ago, you might find that you have to do quite a lot of searching online to get more than a one-word-synonym answer. And good dictionaries provide a context.
So if we forget translation altogether for the present, and concentrate on what you need to read a complex novel or write a letter in your mother-tongue, then it does no harm to use a time-tested dictionary. I personally use two English dictionaries a great deal, a Webster's from 1976 and an Oxford one from the early 1990s. I don't feel I need to be "with it" and "at the cutting edge" when it comes to ephemeral youth slang that will already be dated in twelve months' time. The internet will suffice there.
Then there are books beyond the straight dictionary, such as thesauri (Roget's is by far the most popular) and books that address current usage. Not so much grammar, but a clear-sighted view of the right word. And then there is punctuation. You would be surprised to see how often a comma in the right place improves comprehensibility.
All those dictionaries and other books prevent everything you write becoming a glorified SMS.