Translation:Is the enemy of my enemy my friend?
In my mother tongue (Slovak, yet another Slavic language) the word "vrah" (very similar to the Russian "враг" phonetically) means "a murderer" so you can imagine my confusion...
is the "моим другом" declined this way because it is referring to a state of being, similar to when we talk about someone "becoming" a lawyer etc.?
Well, it is just a fixed usage that "является" should be followed by words in their instrumental case (i.e. моим другом)
"является" means "is", which is used in order to replace "это", and to make a sentence sound more formal.
Является means is? I thought there wasn't really a word for that in Russian??