There is currently no way to reset your own progress in Vermintide 2, however we are more than happy to do it from our end.
Please contact us by clicking the 'Submit a Support Ticket' link in the header, choosing 'Query Type' -> 'Account Reset Requests'.
We will then explain in our response what the account reset entails, and run through the verification process so we can ensure the account belongs to you.
Please be aware that during busy periods (patches, new releases, etc.) we may have to temporarily halt our account reset service.