When you resize an image in Microsoft Paint, it can get blurry depending on a number of things. Images get blurry when resized in Paint if the image size is significantly reduced, especially if the image format is a lossy format or not a bitmap.
To fix this, use a more powerful image manipulation program to resize the image, such as Photoshop or GIMP (a free alternative to Photoshop). Such a program will have a better algorithm for compressing the image on resize.
Additionally, you can reduce the chances