This app was mentioned in 4 comments, with an average of 1.75 upvotes
The easiest way for you @Yucares to interpret this would be like this; a) The world is (nothing) but a treat, and b) The enemy is (nothing) but a mountain. The second one is harder to interpret, and therefore the context of the sentence is important. In this case, it means the enemy is like a mountain, i.e. hard to defeat. Cheers... IF you are interested, Android app to learn peculiarities like this: https://play.google.com/store/apps/details?id=com.upen.learnenglish
I see @TheWorldEdge already corrected this. If you would like to learn Grammar lessons so you can fix these for yourself, check this free Grammar book out - (I had a friend who had similar issues and is now better after reading a couple of grammar books like these - ) https://play.google.com/store/apps/details?id=com.upen.learnenglish
I'm using this one https://play.google.com/store/apps/details?id=com.upen.learnenglish
Not sure if this will help you in any way though
Download a book like this, and read. There is no substitute for reading! https://play.google.com/store/apps/details?id=com.upen.learnenglish
Regards