Render trees with SolidRocks

Hello all, we are architecture students and for a school project we have made a tree (a rubber tree) on a program called speed tree to make good 3DS Max renderings. ( we are using iToo forest to make the forest ) The problem is that we have very little experience on 3DS and we are having trouble making nice looking renderings, probably because we are setting up the cameras incorrectly, VRay lights etc... We have been playing with the parameters and settings for almost 2 weeks, have watched many tutorials but we still cannot achieve the quality of renderings we are looking for...
I don't know if my explanation makes sense, we just don't get the realistic renderings some other stutents are getting... (the problem isn't the floating leaves that you can see on the picture, we can clean that up easily on photoshop) not only are the renderings not esthetically pleasing, they also take a very long time to render... The attached image shows a rendering that took more than an hour, even though the computer used to render has a good processor and graphics card, people around us, other students and teachers tell us that it shouldn't be taking this long, the attached image's resolution is 640x360 so medium quality...
In our distress qnd dispair, we got solidrocks, which is supposed to improve render quality and speed easily even if we don't know VRay perfectly... ( this 640x360 rendering would've taken 3 hours before solidrocks... )
We are wondering if anyone has ever had a similar problem (ugly image that takes a long time to render?) using the same or a similar path as us ( SpeedTree > iToo forest pack > Vray > SolidRocks )
We have been using Vray 3 and 3DS 2015 with SolidRocks version 1.9.5.
Thanks, i will follow this topic/thread closely, please let me know if you need any more information. We are not in a crazy hurry but we need to present our project early december so we are trying to anticipate just in case (in the worst case scenario we can use VRay for Rhino, but we would rather stick to 3DS as we did last time a few hours before the presentation ^^)
Thank you all

Yes here are some wetransfers :

we.tl/KSRtM7qwmL This first one is an archive of a single tree
we.tl/OsEOcEzxkn This second transfer is a litle more messy but it includes an archive of the 3DS file with the one I rendered tests which have failed , images, and so on ...