Blockage in bendy pipe
I'd suggest the following (apologies for the crude drawing). 

From left-to-right:


extend pipe out past the black pipe
attach yellow clean-out elbow (not 90 degree!...use a sweep (yellow))
this will be angled down aiming towards the run along the other wall
connect the sweep to the other pipe using two 45 degree elbows (purple)




Sweep with cleanout: 



45 degree elbow:



That should:


remove any 90 degree turns (never a good thing in a drain)
reduce turns in general (from 5 to 3) 
give you a 'snake-able' cleanout entry point. 


While you're at it, I'd also move upstream to that inside corner 90 degree angle and replace that with a 90 degree sweep as well.