mac os x high sierra desktop background too big

hello,

somehow I must have touch a wrong spot while looking at a pic, all over sudden the pic filled my screen and had to put the mouse to the bottom edge to have the dock pop up.

went to preference> desktop change color the pic is gone but the background of my screen still too large.

tried restart no luck i must have zoomed now the green button have no luck there

no sure how to do this, would appreciate some help its driving me nuts

Thanks