@ferosenfeld said:

The following wikipedia page describes the Gustav serie: https://hu.wikipedia.org/wiki/Guszt%C3%A1v_(rajzfilm) It states it consists of 5 seasons. The current content on tmdb is based on the DVD release that contains only a few episodes from various seasons. Episode list need to be reedited.

There is another wikipedia article about the list of episodes: https://hu.wikipedia.org/wiki/A_Guszt%C3%A1v_epiz%C3%B3djainak_list%C3%A1ja It looks complete but it refers to the IMDB. I haven't found any official Hungarian online or offline information about the exact air dates and list of episodes and seasons.