Explanation
The product type group in the material type controls whether a material is used in the lean service process. The lean service process is a simplified procurement process for services that do not require a service entry sheet or an invoice receipt. You can use product type group 3 (Lean Services) to indicate that a material is used for this process. References: [SAP S/4HANA Sourcing and Procurement | SAP Learning], Course S4520, Unit 4, Lesson 1.

Explanation
To enable partner role determination in purchasing, you must assign a partner schema to relevant document types. A partner schema is a configuration that defines the possible partner roles and functions for a purchasing document such as purchase requisition, purchase order, contract, or scheduling agreement. You can assign a partner schema to a document type in Customizing under Materials Management -> Purchasing -> Partner Determination -> Assign Partner Schemas to Document Types. References: SAP S/4HANA Sourcing and Procurement | SAP Learning, Course S4520, Unit 3, Lesson 2.