Celonis is expanding at a rapid pace, internal processes can be bumpy at times and certain roles are still being formed. This is to be expected at this stage, you can choose to see it as a positive by being directly involved in shaping your path, or you can view it as a negative if you need a very structured environment to succeed.
The people are nice and are invested in their work, but the hiring and pre-onboarding could use improvement in streamlining its process, as well as providing more timely communication.