Facebook quizzes are so seductive. Of course you want to know who you were in a past life and what your decorating style is. The only problem with these quizzes is that they often send spammy messages to everyone you know by posting things on your page at random. Nothing makes friends unfollow faster than feed spam.
You can stop the spam and keep your quizzes by making sure to click appropriately. As soon as you click on a quiz, most of them will ask you, "Who can see updates from this app?" Always click Only Me.
Even though you pick this option, you can still take the quiz and you can still post the results, if you like. When the quiz does post spam on your feed, though, only you will be able to see the post, and your friends won't be bothered.
Did you already do a quiz and it won't stop spamming? Go to Settings > Apps and then click on the picture of the pencil beside the quiz app and choose Only Me or click on the X to delete the app.