How to make the default camera in Blender?

Question

3D

I'm new to Blender and when my work was half done, I accidentally pressed Shift + C instead of Shift + S and the camera in the program became kind of strange, impossible to work with. She stopped zooming in as before, the movements are very sharp, and if earlier she was attached to the object and rotated around it, now she rotates as if around herself. It's unbearable to work like that. I tried Ctrl + Z and Num5 - nothing helped.