On the heels of the couple’s engagement announcement on Monday night [Apr.4], Blac Chyna and new fiance Rob Kardashian have been overloading our social media timelines with their highly amusing Snaps, and on Wednesday, Chyna propositioned Kardashian with an intense five-week fitness challenge, and he happily accepted.   #PressPlay: Aww #BlacChyna really has #RobKardashiam coming out of his shell! #BaeWatch A video posted by The Shade Room (@theshaderoominc) on Apr 6, 2016 at 6:39pm PDT   Chyna declared that she would be training Kardashian over the next five weeks leading up to her birthday, and she added that she would be documenting the journey. True to her word, she put…