I misunderstood my teacher and accidently installed "Microsoft Windows Server 2019 Standard" on my laptop instead of in VirtualBox. Will someone please guide me through how to get back Windows 10? I have tried to search for help everywhere with no success.
My guess is that I need a flash drive with Windows 10 on it.
Sounds like you installed Server 2019 core only. If you wanted Desktop Experience then boot the installation media again, delete / recreate partition and choose the option
If you wanted to reinstall windows 10 then boot from the pc recovery media, delete / recreate partition and follow the prompts. Another option is to download the media here but check with the OEM provider to see that product key channel aligns with this media source.