First of all thank you very much for using the pro version of the theme.
Now since you have set the slider using the category option, please make sure to upload the image in featured Image section of each post that you have assigned to the category which you have chosen to display in the slider.
As for the other section, you have to enable the sections you want by going to Admin Panel > Appearance > Customize > Homepage Sections > Manage Sections. You even can sort the section as per your requirement from here.
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