Windows/Ubuntu dual boot - no option menu, immediately boots Ubuntu

Question

This would be a duplicate question if any answer in this question worked for me. So here is what I did so far:

1. I created free space on the disk using the windows disk management tool
2. When installing ubuntu, I selected the "other" option since tutorials were advising against the automatic "install ubuntu alongside windows".
3. I created a / partition and a swap partition. And clicked continue. And followed the rest of the Ubuntu installation steps.

Now whenever I start my PC, ubuntu is immediately booted. So according to the already mentioned question I tried:

1. Opening /etc/default/grub I found this:

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

2. So I tried changing GRUB_TIMEOUT_STYLE first to menu and then (since that did not work) to countdown. In neither case I would get a menu. Before restarting I would use: sudo update-grub and get

Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.3.0-28-generic
Found initrd image: /boot/initrd.img-5.3.0-28-generic
Found Windows Boot Manager on /dev/sda1@/EFI/Microsoft/Boot/bootmgfw.efi
Adding boot menu entry for EFI firmware configuration
done

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Other remarks:

• This is my first time installing a linux distribution so I barely understand what I am doing, but I tried to double check everything. And I am very sure that I haven't touched the windows partition during installation. And starting windows still worked after reducing its partition to get free space.
• The ubuntu log in screen is extremely laggy. This is probably independent from this problem but I thought I should mention it. I intend to try out suggestions from here after fixing this problem.