This is the 2882nd most frequent Polish word.
mającego
"Having" or "possessing."
The word 'mającego' is used as a participle describing the teacher, indicating possession of great knowledge.
Uczniowie podziwiali nauczyciela mającego wielką wiedzę.
The students admired the teacher who had great knowledge.
The word 'mającego' modifies 'autore,' describing a known characteristic related to the author.
Kupiłem książkę mającego autora na listach bestsellerów.
I bought a book whose author is on the bestseller lists.
Here 'mającego' is used to indicate possession of a good mood, connected to the worker.