Applying materials without it being stretched

I think I just use Basic > Cube for the walls. I tried making a new map but now I am just editing the default first person map.

I dragged and dropped the grass material on the floor and I noticed it is stretched (same for the walls btw). How exactly do I make it ignore the stretch of the brush/mesh? So the material/texture keeps being at a 1:1 scale no matter how I drag it later on?

Thanks and sorry for the noobish-question, it’s probably gonna take a while before I get used to this editor.

://i.imgur/7qCVwR6.jpg