Hi, Neel Rajendrabhai Patel!
Welcome to the Microsoft community and thank you for asking your question in the community!
According to your description, I understand that you have encountered the problem that Windows Boot Manager cannot start Windows normally.
This situation is more complicated. It is usually caused by the damage of the boot file. The general repair method cannot completely guarantee the safety of your data.
And you have an upcoming exam, and you don’t want to lose any of your data.
My suggestion is that you go to a nearby repair point to fully back up your data, and then perform a new installation of the system. This is the safest guarantee for your data.
Thank you for your understanding and support! Please let me know if I have misunderstood. Tell us the results and we will get back to you as soon as possible. We look forward to hearing from you.
Best regards,
Yang.Z - MSFT | Microsoft Community Support Specialist