If you are experiencing this issue, it could be a problem related to the aspect ratio settings of your graphics card.
Depending on your card:
Right-click on your Desktop and select NVIDIA Control Panel. From there go to Display -> Adjust Desktop Size and Position -> In the Scaling tab change scaling method to Full-screen.
Please try changing the scaling from "Display" to "GPU" in the Nvidia Control panel.
HERE is an official AMD guide how to do that
Please open Intel Graphics Control Panel, then make sure to select Scale Full Screen. THIS image could be handy:
Alternatively, using an unusual DPI setting has been also known to cause these problems for some games. Please follow these steps to reset it to the default value and let me know if it helped:
I) Right-click an empty section of your desktop and go to "Display settings",
II) In "Display settings" window locate ""Scale and layout"" and select the 100% value. Press Apply to save settings.
III) In some cases it might be also a good idea to have a look at the "Advanced scaling settings" section.