Slider pictures have different size

Hello, the slider images are shown in different sizes. I have tried to resize them to the suggested size, but still they are shown in different sizes. The set up for both pictures is the same. Can you please tell me how I can manage it, that they are shown in the same size in the slider on the homepage? Also why do some of the features images automaticall croped and some not? Is there a way to set up the same size for all? Thanks in advance!