Help in reducing Assamese spelling mistakes and fine-tuning sentence construction.

I study in class 9 and have my Assamese exam in a few days. I need to improve my sentence constuction and reduce the amount of spelling mistakes I make within these few days. My school's board is ICSE. We have কাৰেঙৰ লিগিৰী and সাউদৰ পুতেকে নাও মেলি যায় in our course. Is there a solution to my problem? I had posted tje same question in several sites like Quora, Meritnation, etc., but received no reply. I would also be grateful for any tips to increase my marks in Assamese.