This is the 4535th most frequent German word.
professionellen
"Professionellen" means "professional" (adjective) or "professionals" (noun, plural).
The word 'professionellen' here is used as a descriptive adjective in its dative singular feminine form to describe the teacher.
Der professionellen Lehrerin gelang es, die komplexen Konzepte den Schülern verständlich zu machen.
The professional teacher managed to make the complex concepts understandable to the students.
The word 'professionellen' here is used as a descriptive adjective in its accusative singular masculine form to describe the photographer.
Er beauftragte einen professionellen Fotografen, die Bilder für seine Webseite zu erstellen.
He hired a professional photographer to create the images for his website.
The word 'professionellen' in this sentence is in the dative singular masculine or neuter form, modifying the word 'Rat' (advice).