I have a text in my learning materials as follows:
彼ら は 自分 の 事 しか 考えて いません。
Its translation is apparently "they only think of themselves".
Now it all makes sense to me until the ません at the end. To my mind it negates the entire sentence. So it means that they DON'T only think for themselves. However, obviously that isn't the case.
If anyone could clear this up, or give me resource for it, that would be amazing. My Japanese level is elementary at the moment.