The point of the encryption is to make it a lot harder to make sense of what's inside the data volumes when you don't have the decryption key.
It's not about "user-land' encryption, table access permissions, encrypting columns or anything like that.
Think of it as a big padlock on the box called 'your database'. To open the box, aka to start the database, you need the key. You need this key only at this point in time - simply to 'open the box'.
But once the box is opened (that is your SAP HANA instance is running) then you can use it as you always used it. No difference there.
That is BTW the same way, encryption works for Oracle databases. Once the database is up and running, the users can access the data and don't need to think about the whole decrypting process.