SOAP to Proxy & Proxy to SOAP scenario in SAP PI

Dear Experts,

I am new to SAP PI, we have requirement like 1) to capture the details of RFQ from Webservice and post the details in SAP ECC as Proxy by Asynchronous mode of communication. 2) Conversely from SAP ECC the respective Quote ID & other details of RFQ should be poested back to the Webservice. Here I need to build to 2 interfaces one for request and other as response for that first one by Asynchronous mode. ABAP team would be our organisation itself but I need to know the inputs required from Webservice[client] team.

Kindly guide me the questions/inputs I require from the Webservice team to start working ?

Thanks,

Ramu.