It is the main problem of All operating system in virtual machine which can not adjust according to the screen.
When you install macOS Catalina on virtualbox on windows after the installation is completed then you may might face a problem and issues, we always try to find out a solution for very errors in virtual machine when you use macOS 10.15 Catalina on virtualbox, one of the problem on the virtual machine is the screen resolution which you need to fix them according to the screen you use.
