Obviously, Orks fight other Orks all the time. It's the main reason Orks haven't taken over the galaxy. That being said, are Orks capable of making friendships, not necessarily close caring friends but more like tag team wrestling partners always wanting to do stuff together etc? Seeing the trailer for the Orks in BFG:Armada singing and chanting make me think that there can be SOME comradery. Having not read any of the books out there I have no idea if this has ever been touched on.
As comrades, yeah. Dawn of War II Campaign can attest to that. As buddies that socialise and share a fungus beer? No idea.
Not really. Orks will usually end up back stabbing whoever they worked with. Orks cant even get along with other Orks.
Easiest way to answer this with a citation of lore material is the Sanctus reach book. It has a story of a big mech and his buddy doing all kinds of pal type things. Orks have social circles and water cooler talks as well. They just talk about other stuff like "hey did you know you got a knife stuck in your arm?" "Hurhurhur oh so I do!" "Classic gobsmash dat is"
Not my fault you overgrown fungus-children can't behave yourselves and constantly have to fight each other over primitive things like teeth.
Would it be better if we destroyed entire planets over varying interpretations of religious beliefs that the deity they were about would hang his head in shame for?