QGIS has an, in many ways, recommendable approach to language. By default, it uses the language of the system it is running on. However, many learning resources are in English, so it is probably easiest to learn QGIS by changing its language to English.
For demonstration purposes, I will here change the user interface from English to Danish
From the Settings menu (instillinger in Danish) Choose options (instillinger in Danish)
In the general tab (Generelt in Dabsih), tick the box Override System Local and in the “User Interface translation”, choose the language you wish to use.
NB ! the changes first take effect after restarting QGIS.