"Dogs are my friends!"
Translation:Собаки - мої друзі!
Собака is masculine. But it doesn't matter. It's not about the gender of a noun, but the gender of a creature. But even this doesn't matter in this case.
Друзі is what you say about a group of people (or other creatures) of any gender. Подруги is about exclusively female group. This sentence is about dogs in general, not about some particular dogs of some particular gender