The recommended image sizes are

Post featured image  ( With sidebar)

Width: 750px;

Height: 400px;

Aspect ratio:15:8

Post Feature Image (Without Sidebar)

Width: 1140px

Height: 500px

Aspect Ratio: 57:25

Slider Image

Width: 1920px

Height: 650px

Aspect ratio: 96:25

Page featured image ( with sidebar)

Width: 750px;

Height: 400px;

Aspect ratio:15:8

Logo:

Width:182px;

Height:82px;

Ratio:91:41