There are a few things you can do to make Kali Linux faster in virtualbox.
Allocate more RAM to Kali Linux in virtualbox settings.
Use a faster virtual disk.
Increase the CPU priority for your VM.
Turn off unneeded services.
Use a lightweight desktop environment.
Use a faster networking interface.
A higher screen resolution will use more resources and slow down your VM. Try a lower resolution for better performance.
Use the Kali Linux minimal install.
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