Hello ahmedmae94,

If You use the metal cable tray, I suggest You instalation of metal partition in mentioned cable tray. The shield grounding on both ends of Profibus cable is obvious. This distance of metalic Profibus bring to You limitation of transmission rate to 187.5Kbps.
Use of fiber optic - FO cable instead metalic cable is better solution - non reduced transmission rate and high resistance against electromagnetic interferences and disturbances. Use of FO also can solve possible problems with balancing ground currents between far objects, which can flow by shield.
Use FO and OLM (Optical Link Module) offer You made star topology.
And finaly the answer to Your last question You can find for example here:

http://www.procentec.com/profihub/b5/en/index.php

Vitas