Creating a webservice using the webservice tool and consume it in sharepoint

Hello everyone,

I am trying to achieve the following:

I want to create a webservice using the webservice tool. This webservice should return the recent activities to a given contact person (I call the service with the ID of the person and it returns all activities related). This webservice should then be added to our sharepoint server using visual studio.

I have general knowledge on how webservices work and how to consume them in visual studio and sharepoint.

My problem is that I have very little knowledge on how the data in sap crm is accessable. Could someone guide me to through the process of creating such a webservice?

Thanks in advance,

Moritz