Hello, Shubhada Baikar

Improvement exams are conducted for the students who have passed their exams but unsatisfied with their performance and willing to reappear and do better 

CBSE improvement form start date will be in last week of Octobor 2019 and last date of submission will be 2/3 week  November 2019 

Exams will be conducted between 2/3 week of Feb 2020 to 1 week of April 2020

Declaration will be in August 

If you want to fill improvement form you can't engage in higher studies you have to study as a droper 

Hope this helps you if you have any queries you can add in comment section 

Good luck!