No option to boot into ubuntu after windows update

Solution 1:

Thank you for all.
I fixed my problem by boot-repair, here is a quick guide for those who are having similar problem:

Fix GRUB

• Insert Ubuntu Media into your pc.
• Shutdown your pc. Then turn it on again, Pressing Option Key (MacOS) F12, F11, DEL depending on your PC.
• Select the Ubuntu media.
• When PC boots, do try Ubuntu.
• After you land into desktop, Press CTRL+ALT+T to open a terminal.
• Now type the following commands:
  

sudo apt update
sudo apt install boot-repair
boot-repair

• Now repair your GRUB.
  

After its repaired, Shutdown your PC, then the Ubuntu should boot, as usual. If not try making "ubuntu" default in BIOS settings. I cannot instruct this because it depends on your PC.