I accidentally deleted a partition that probably was the one with the os I was using. Now it shows this. How can I regain access to my Computer? I did a dual boot of Ubuntu 18.04.1 LTS with WIndows 10.
Since you indicated you only have a mobile phone and it's unlikely you will have access to the ability to create a new DVD or USB disk, here are some tips you can try from the GRUB console:
First, you need to set "pager" mode in GRUB so that you can read the output of commands if they go off the screen:
grub> set pager=1
Next you want to see what disks GRUB can see, if any:
This will output something like:
(hd0) (hd0,msdos2) (hd0,msdos1)
Here it's showing there are two partitions on
(hd0) - if there are no partitions listed then you somehow deleted your entire disk or all of it's partitions. If there are disks there you can try accessing their contents:
grub> ls (hd0,0)/
You might see output that looks like a Windows disk, assuming it has a
C:\Windows directory and a
C:\Users directory (note the
C:\ wont be displayed by GRUB) and you can follow these instructions to tell GRUB to manually boot that partition:
Did that partition contained both Ubuntu and Windows10 ? You cannot install Ubuntu and windows in the same partition. In that case you can get access from the other OS.
Anyway,if that is not possible, the easiest solution seems to be reinstalling Ubuntu 18.04. I hope you have the live USB or DVD of Ubuntu at you installed earlier. Just insert it and enter the bios. Boot from USB/DVD and install it. You will be fine. After installing Ubuntu you can dual boot it with windows10 if you wish.
In case you don't have live USB/DVD, you can use your phone as a bootable device :