Not all the assets you download from internet will be compatible. In your case you can either scale the minotaur up in the game engine(which should be the proper way of doing this imo). Or you can resize the sprite sheet. As a rule, you can only resize pixel art assets with powers of whole numbers or the assets will lose quality. This site helps you resize them without quality loss: https://lospec.com/pixel-art-scaler/
Hope this helps!