What does it mean when you dream that a friend's pitbull dog is barking at you?
This dream probably refers to some criticism you have received.
The dream presents a literal image of the idea that someone is
constantly "barking" at you.
The usual explanation is that a dog is barking somewhere nearby, so your mind incorporates that sound into your dream to prevent you from waking up. Symbolically, because dogs bark to warn the pack (their owners) of danger, your dream might be a warning to be careful of making foolish choices that could expose yourself to trouble.
Assuming that by "together" you mean that the dream was about the friends in a romantic relationship... it expresses your own thoughts and feelings about your friends. You might suspect that they admire each other or you could sense intuitively that they would make a good couple. Or, if they are not friends with each other, the dream might show how you wish they could be friends with each other the way they are individually…
Without more information about the dream itself, an accurate interpretation is impossible. The dream could be part of the grieving process for the friends who have died. Another possibility is that something during the day, such as a piece of music, a certain place or even a particular odor, may have triggered the memory of the deceased friends, and the memory brought about the dream.