Ack! I once remember reading this hard yaoi manga once but my compy crashed.Basically the story is about this student? who is used to be being seme with his partner, but he comes too fast, leaving the other sexually frustrated.So partner gives gives student this porn video and the student sorta falls for one of the porn actors and is inspired to learn from them? He goes to the porn company and is accepted and basically has sex with the two guys from the video but ends up with the one he liked from the start? Oh and he has a threesome with the two of them like in the ending chapters or so? They are also all filmed course they are all porn actors? Also, I remember the camera man and the manager are also in a relationship and that the cameraman is called Josh and is the uke depsite being all muscular and stuff in the relationship.Thank you very much! I would appreciate very much if someone helps!

It's Ikenai Otoko by Kamuro Akira (mangaka) and Takao Hiroi (author).
I really like that manga, hehe.

Oh, and there's this guy who appears in the Ikenai Otoko extra - he's a main chara from Himitsu no Kuchizuke, which has a sequel Rumble Rush, Of course you can read Ikenai Otoko without reading those other two, but if you like the story and curious about that man from the extra, I suggest cheking the "prequels", too.