Hi Jun,
Welcome to Microsoft Community. According to the Microsoft Store the keyboard layout for Surface in Czech Republic is: QWERTY(INTL). As with the standard QWERTY layout, accents, umlauts, etc. are entered via the AltGr key or key combinations. Surface accessories | Microsoft Store Compatible keyboards for Surface Go 4 are not available in the Microsoft Store. You can refer to this link to visit a Surface dealer to purchase one. Seznam autorizovaných prodejců společnosti Microsoft — Surface Business
Your Sincerely Hahn. W - MSFT | Microsoft Community Support Specialist