So I was trying hyperledger fabric private data collection feature, but since I'm a beginner, I don't know how to make that only the owner has access to his data and not the entire Organisation
There is no direct way in fabric to do this. Collections Config only supports it at identity groups level
You will have to add necessary rules in your chaincode while querying and make your data aware of the ownerId
While storing the data You can add a field to your data called OwnerId stub.GetCreator() can be used to populate this field
While querying the data In your chaincode, validate the OwnerId field with stub.GetCreator()