I am the Tenant-Manager of the campsite since 2002.

You could become a front-of-house manager, for instance.

the profit-making company which has become the lessee-manager can deduct the lease payments and the operating loss for the business from its profits.

As the renter (locataire-gérant), you must be qualified to run the business and must run it as it is (i.e. you cannot change the nature of the business at all).