Hello Aspirant

There are two options available to you:

The first step is to just retake 11th grade, pass the course, and comprehend the concepts once more because 12th grade is built on 11 concepts.

The second one is purely private but is once more only requested by the relevant school authorities.

Also, Don't rush, though, and think things  before making a choice.

And if you repeat, it will take you an additional year, but the best students from that class will only be selected.

Hoping best for your future.