How do I update my kernel header?

[Tomek]

Old, unsupported kernel, same as I described moment ago here

Error: VirtualBox Linux kernel driver is either not loaded or not set up correctly

You use old, unsupported kernel – that’s why you cant install proper modules and drivers. Remove 5.9 and install one of supported kernels: available kernels: * linux414 * linux419 * linux44 * linux49 * linux510 * linux513 * linux514 * linux515 * linux516 * linux54 * linux510-rt * linux515-rt