How do I make everything smaller?

Help me! I just build a lot of terrain and buildings and stuff, and then I added my first person controller. But then I noticed that I had made everything to big. The First Person Controller was like an ant compared to the buildings and terrain. I tryed makin the FPC bigger but then it just took supersmall steps and it didnt work. Then I tryed selecting everything and make it smaller with XYZ but then everything turned into cubes. Please help me! Is there a way to make the FPC footsteps longer or somthing? Just anything! Thanks.

Parent all of the environment to an empty GameObject. Change the scale of the GameObject, which will also change the scale of the children.