Hello samroza,
Thank you so much for using our theme. We have a detailed documentation here.
For making the image site suitable for our theme, please follow the below process:
First, go to Settings > Media
Set thumbnail size : 500 * 280
Set Medium size : 690 * 400
Set Large size : 1080 * 530
Click on Save Changes to save the change.
We recommend you to use plugin named Acme Fix Image
to crop the actual size of the images.
After installing this plugin
Login to admin panel,Go to Appearance => Acme Fix Images.
Check the image sizes you want to fixed
Click Fix All Images.
Hope, the above procedure will easily solve your problem. If problem remain as it is, please feel free to ask.
Thanks