I think you are talking about NEET. Now as you have a weak background in the portion of 1st PUC then it will be difficult for you to coup up with the syllabus in the short time. But this doesn't mean its impossible for you. You have to try in a specific way to combat this situation. I would recommend you to emphasis on problem solving more than that of theory. BIO can be a bit tough for you to memorize or clear the concept but with trying I hope you will be able to do that.

For NEET preparation tips you may follow the link provided below:

https://medicine.careers360.com/articles/how-crack-neet-in-first-attempt#:~:text=The%20mock%20tests%20should%20be,exam%20and%20the%20important%20topics.

I hope this answer helps. All the very best for your future endeavors!