That error does not sound like anything Linux. However, it does sound Windows’ish. I think I’ve seen it before. I suspect Windows did an upgrade an overwrote grub. Or something. It has happened before, after all.
I think you need to follow this guide:
https://wiki.manjaro.org/index.php/GRUB/Restore_the_GRUB_Bootloader
And here’s something about dual-booting just for interest’s sake:
Difficulty: ★★☆☆☆
Hope this helps!