against
The German word 'gegen' is used to express opposition or contrast to something. It can be used in a variety of contexts, such as 'to be against something', 'to fight against someone or something', or 'to argue against a point'. It is important to note that 'gegen' is often used with the accusative case, which means that the noun following 'gegen' will change depending on its gender and number.
I am against this idea.
In this sentence, 'gegen' is used to express opposition to something, namely 'this idea'.
He ran against the wall.
Here, 'gegen' is used to describe a direction or target of a motion. In this case, 'the wall' is the object the subject 'he' collided with.
She played against her brother in the final.
In this context, 'gegen' refers to competing against someone in a contest or a game. The competition is 'her brother' in the 'final'.