Not loading images and doesnt seem responsive

I’ve tried several ways at an attempt to create a flipbook with this plugin…Would purchase plugin if this could be sorted quickly…I uploaded image sizes 850×1101 to create a newsletter flipbook but flipbook is so slow to load it just doesnt…I then resize images to 450×550 and still no load…When I change settings in flipbook to 400×400 where it states leave blank for responsive – the flipbook appears but hangs past the border and does not look good as to one of the pages is completely off screen..Attempted to double the size to get both pages on my page…Any quick help would be appreciated.