La traducción más literal sería " Colega " pero depende de la zona porque en Madrid por ejemplo podría traducirse también como "tronco"

Yes of course there are other ways to say friend in spanish, but it depends of the the coutnry where you were, for example here on Peru you could say: "somos patas" it means "we are friends". Also you could say "Habla, causa" this means: "hey, dude!", and there are a lot more, just ask me if you want to know.

In spanish there is no real word for dude or buddy, the words that are similar are actually vulgar or make no sense. Now we have different words to call our friends but that varies on the country and is used when refrencing your friend not really when your talking directly to them.

that depends of country.