The creator of a work does not receive any license payments dependent on turnover or profit; he is to be remunerated by a one-time license payment (flat fee) for his performance.
Whether this is legally permissible, or whether the author can demand, for example, a piece participation because of his legally guaranteed right to appropriate remuneration, depends on the circumstances of the individual case, in particular on what is found to be customary and fair in the respective industry.
In the film and photo industry, the flat fee is often used.