So, this has been bothering me for a long time, but what case should you use when dealing with two nouns in a row. Like if you were to say "x is y" (Джон актер). But, if the direct object is animate, like an actor is, wouldn't it be "Джон актерa"? Same with "Я твой друг". Since friend is an animate thing, why isn't it "Я твойего друга"? What is the correct way to say that "x is y", even if the y is animate!
There are no direct objects in your examples,
твой друг are actually predicates or, to be more exact, nominal parts of the compound nominal predicate. The verb 'to be' which is usually omitted in Russian when it is in the present tense is intransitive, so it cannot have direct objects. The nominal part of the compound nominal predicate is usually in the Nominative case, never in Accusative, so
Джон актер. and
Я твой друг. are absolutely correct sentences and that's the only way you can say it.
In the sentences like "X is Y" Y is never used in accusative. So, the right form is "Джон - актер" (long dash is usually required if the subject is a noun). But, however, you can (and must in non-present tenses) explicitly specify the "to be" verb, then the predicate will be in instrumental case: Джон является актером (John is an actor), Джон был актером (John was an actor)
A lot of the time communicating in street russian is about whats unsaid. It takes many forms. It flavors communication in ways that only can be compared to syncopation in music.
The missing bits get derived from the context and/or from non-verbal communication. Facial expression. Tone. Vocalization. Even wider cultural context.
"Джон актёра" literally means "John did the [male] actor". Same as in english it might mean intercourse, it just as well might mean homicide, as well as many other things :)