The Personal Data Flow from the Data Subject via the Controller to a (sub) Processor up to cleansing/deleting. Having an overview of Personal Data at hand is paramount. Check for practical solutions: technical and/or organizational measures. The Flow in a picture:

from Data Subjectwhataction by
DPIA / GDPR by designPNO
Privacy StatementPNO
Cookie PolicyPNO
General Terms & ConditionsPNO
ContractPNO / Client
Shared responsibilityPNO / Client
Consortium AgreementClient / PNO
Processing AgreementClient
via Controller
Processing AgreementPNO
Audit PNO / Processor
to Processor
Processing AgreementPNO
Audit PNO / Sub Processor
to Sub Processor
and CleansingAnonymise DataPNO
finish Cleaning upDeletion DataPNO