Dual boot doesn't load Debian/GRUB anymore only windows

Question

I have a Dell Notebook with Windows 10 installed. I installed debian about 4 months ago making it a dual boot option. Have been using debian daily, everyday it shows me the GRUB and auto loads into debian. Yesterday decided to go into windows, just selected windows in GRUB, now I can't go back into debian.

I shutdown/restart and always loads windows. It doesn't even show me the GRUB. The boot loader first option is debian and the second windows boot manager, nonetheless it doesn't load debian.

Already tried:

• Manually choosing the debian option in boot loader (f12)
• Disabled secure boot.
• Tried windows recovery options > advanced restart
• Was about to remove windows boot loader from boot options but BIOS didn't allowed me to.

What else can I do?

EDIT: Well, I decided to follow these instructions and now nothing boots anymore, neither debian or windows... This is the command:

bcdedit /set {bootmgr} path \EFI\debian\grubx64.efi

EDIT 2: As requested this is the output of sudo parted --list

user@debian:~$ sudo parted --list
Model: ATA WDC WD10JPVX-75J (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system     Name                          Flags
 1      1049kB  525MB   524MB   fat32           EFI system partition          boot, esp
 2      525MB   567MB   41.9MB  fat32           Basic data partition          hidden
 3      567MB   701MB   134MB                   Microsoft reserved partition  msftres
 4      701MB   1488MB  786MB   ntfs            Basic data partition          hidden, diag
 5      1488MB  834GB   833GB   ntfs            Basic data partition          msftdata
 8      834GB   846GB   12.0GB  linux-swap(v1)
 9      846GB   991GB   145GB   ext4
 6      991GB   992GB   979MB   ntfs                                          hidden, diag
 7      992GB   1000GB  7892MB  ntfs            Microsoft recovery partition  hidden, diag


Model: Sony Flash Disk (scsi)
Disk /dev/sdb: 16.1GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  16.1GB  16.1GB  primary  fat32        boot, lba

Answer 1

I would try to redo the GRUB Installation process (if at least grub seems to load, you can skip step 3):

1. boot from a linux live iso (e.g. debian live iso)
2. mount your efi system partition: mount /dev/sda1 /mnt
3. grub needs devices: mount --bind /dev /mnt/dev
4. chroot into your debian system: chroot /mnt
5. reinstall grub entry in firmware boot manager: grub-install --target=x86_64-efi --efi-directory=/mnt
6. let grub detect the installed operating systems (if I remember right grub should output the detected operating systems): grub-mkconfig -o /mnt/grub/grub.cfg

https://fosswire.com/post/2009/05/restoring-overwritten-grub/