While Stardew Valley supports many languages officially, it does not yet include a native Czech (CZ) translation. However, the dedicated Czech community has developed a high-quality fan localization that you can download and install manually to enjoy the game in your native language. How to Download and Install Stardew Valley CZ
To get the Czech translation working, you must use a modding tool called SMAPI, which allows the game to load custom files. A Guide to Modding Stardew Valley in 1.6! stardew valley cz download