Reply to Nifty Fifty

Hi I am experimenting with the nifty fifty lens but I am wondering what I did wrong with this photo people in a park , i realize I am not using a zoom lens but is there a way of sharpening the image background or was I am out of focus in the first place

second photo was taken with same lens horses in a field,the photo was more in focus

Thanks

flic.kr/p/2jMf3GV

flic.kr/p/2jMf8qC