through
The German word "durch" is a preposition and adverb that can be used in various ways, similar to the English word "through". It can indicate movement or location, such as "going through a tunnel" (durch den Tunnel gehen) or "looking through a window" (durch das Fenster schauen). It can also express completion or a cause-effect relationship, such as "finish something through" (etwas durcharbeiten) or "because of something" (durch etwas).
I am walking through the park.
In this sentence, 'durch' is used to express a movement through a certain place. It's a two-way preposition, which means it can be used with both accusative and dative cases, depending on whether it's a movement or a state, respectively. Here, it's used in the accusative case indicating a movement.
Please look through the window.
Here, 'durch' is used to indicate looking through something transparent. In this usage, 'durch' is followed by an accusative object, in this case 'das Fenster' (the window). This signifies the path or direction of sight.
We learn through mistakes.
In this example, 'durch' is used in the sense of 'by means of'. It's indicating the means or method by which the action (learning) is completed. In such uses of 'durch', it's typically followed by a noun in the accusative case, here 'Fehler' (mistakes).