I have an issue with my screen size as it is way to small as can be seen in the appended image. I have already installed guest additions and tried out different resolutions but that didn't change anything. Can anyone help me to get the correct size?
tried out different resolutions You didn't mention that what you tried (You tried in Virtual Box or Kali). If you tried by changing virtual box resolution than try to change resolution in Kali. Change resolution in Virtual Box also. Virtual box's resolution and Kali's resolution should be matched with your laptop screen size. Otherwise you will face issue with your screen resolution that's what you are facing now. Nonetheless, if you are facing the issue than comment below I will provide a YT video cause, when I was using Virtual Box. I noticed that Virtual Box always can't detect your screen size. That moment you have to try something else.