Hello TabyP,
I don’t know the theme you used “Sensible-wp” but when you load the images it should allow you to set some parameters such as: left, right, alignment to the center or adaptation of the image to the available space.
What you notice on the monitor and that only a part of the image is displayed, on your smartphone you can easily notice the differences.
I don’t think your problem can be traced back to a problem with non-responsive images. WordPress is responsive, and so is your theme.
You need to work on the format and size of the image or use another theme (Enfold) that can help you solve these difficulties.
Paolo