It’s not necessary, but it is recommended if you don’t speak Chinese. Except for the most visited section of the Great Wall, Badaling (which can be reached by train), reaching the Great Wall is by no means simple, as you will have to take at least two buses (and the second normally isn’t easy to find), which means that it is advisable that you rent a private vehicle or go on a tour to visit it.
The majority of hotels and hostels can organize this visit, and many of them also offer tours, but if you want to plan it beforehand, you can contact us and we will recommend a good travel agency for the trip.