In the first screenshot, it shows you downloaded a Win10 OVA file, which needs to run inside VirtualBox according to the lectures you likely (?) have already watched. I see that you afterwards installed VirtualBox and tried running the Virtual Machine.
Not sure the problem as there really isn’t enough information. I recommend this: reboot your computer, open VirtualBox, select the Win10 VM, choose Settings -> General -> Basic -> Version -> choose Windows 10. Go to Display-> Video Memory and set to the maximum (128 MB?).
Try running the Windows 10 VM again and report back.
Edit: in the screenshot that shows Windows 7 in the dropdown box, it’s clear by the scrollbar on the right that you can arrow down further. It seems that Windows 10 should be just below.
Also make sure in the settings of the VM you have the correct 32 bit or 64 bit chosen according to the OVA downloaded.