As there is quite a confusion regarding this children show I'm leaving here a few notes about current episode structure. Due to lack of official sources (the series was created in 1957) the primary source is currently Czech wikipedia which did quite a comprehensive research and as of today (2019-02-14) claims there are 49 unique episodes. Other sources claims there is more episodes (up to 64) mostly because:

1. They also count 12 "episodes" from 1998, which are in fact just bonus shorts from DVD release (0:33-1:15 minutes long) and thus here on TMDB these are put in Season 0 (Specials) according to TMDB contribution bible
   
2. The episode named "Krtek a myška" (The Mole and the Little Mouse / Der Maulwurf und das Mäuschen) is the same as "Krtek a potopa" (The Mole and the Flood / Der Maulwurf und die Überschwemmung), latter being also from DVD bonus from 1998 mentioned above.
   
3. The episode named "Krtek a maminka" (The Mole and the Mother / Maulwurf und die Mama) is the same as "Krtek a porod" (The Mole and the Birth / Der Maulwurf und die Geburt).
   

If you find any other sourced information regarding this show, please leave note to the mods and it could be updated.