ahmet,
This is a common scenario. Many manufacturers will outsource their 3PL (warehousing and transportation) activities.
In SAP the manufacturer will create sales order and delivery. The inventory will be maintained in SAP, plant and storage location.
1. delivery information from manufacturer to 3PL :
Once the delivery is created, via interface this information will be sent to the 3PL system. They will do the 3PL activities, once the truck has left the warehouse.
2. pick, pgi information from 3PL to manufacturer:
An interface will send information with picking and PGI. When this inbound to SAP message is processed, the delivery will be picked and PGI. The inventory will be reduced accordingly.
After delivery process is over, then the next step i.e. invoicing will take place like it generally does. It can be done manually by VF04 or automated by setting up a daily (night) job.
TW