Ubuntu 18.04.2 LTS | Restart and select the appropriate boot device or insert a boot media when attempting a dual boot

Here is the tutorial that I went to double boot: youtube

Here are the steps I took to get where I am now:

  • resized a partition for ubuntu to install on
  • become quick start of this thing
  • downloaded the ubuntu ISO
  • created a bootable USB stick with rufus
  • booted from a usb memory
  • accidentally pressed try Ubuntu without installing or something like that of the GNU GRUB
  • I tried to download ubuntu from the inside.
  • The type of installation that I chose is anything else Because I want a dual boot between Ubuntu and Win10
  • created an exchange area (I do not know what it is for) and a Ext4 partition with "/" as the mount point
  • Then I pressed Install now, but it gave me a warning that I did not have an efi partition of some kind (but in the tutorial it was easy for him)
  • pressed continue without creating an efi partition
  • then he filled the rest of the things and waited for Ubuntu to complete the installation
  • then the installer crashed …
  • it would not close if I tried, so I rebooted the PC (note that the USB stick was still on)
  • He showed me the GNU GRUB again and I chose to install Ubuntu from there
  • clicked delete ubuntu and reinstall and did the same things
  • finished and told me to reboot and everything was fine because I created the efi partition from the main partition
  • he did not tell me to remove the USB stick like in the tutorial and he showed me the GNU GRUB again with ubuntu test without installing Y install ubuntu Y OEM install
  • Then I rebooted the PC and removed the USB to see what happens, but I just gave Restart and select the appropriate boot device or insert a boot media
  • and now I'm stuck with ubuntu and I do not know how to go back to win10

I tried to see the boot order, but there was only one thing there. assuming it's the hard drive

Can anyone tell me what to do to get back to Windows or dual boot?

Any small help is appreciated.
and sorry for the long explanation, and if you need more explanation, just say ^^.