I try to make a game in Unity 2d. But when I drop the image in Unity the image size increases 3 or 4 times. Can I fix that or is this normal?
The default sprite size in Unity is 100 pixels per unit.
This means that if you have a sprite that is 100 pixels wide, it would occupy "1" Unity unit. If you moved this sprite to the left by 1 unit, it would shift 100 pixels to the left.
You can change this value by selecting your sprite, and changing its "Pixels per Unit" property.
I typically set my sprites to their native size, for example, if a sprite is 64x64, I set it to 64 pixels per units.