Short term

Can you please tell in which stream you wish to do short term courses? If you are looking for short terms courses in beauty and fitness, you can join certifications like Professional Make Up, Diploma in Dietetics, Health and Nutrition, Foundation Course in Beauty Therapy, etc.
You can refer to the below mentioned links to know about the colleges and their fee:
https://www.shiksha.com/beauty-fitness/colleges/colleges-india

Hello Kaushik,
Short terms courses should be in such a way that you learn something useful for your undergraduate degree.
As you are going to pursue B.Tech computer science, it is better to learn the programming languages as they form the basics of all software and object oriented programming.
This will be easy to learn in this short time also. Then, you should get updated with the latest technologies and those will not be taught to you.
Computer science is a competitive course so you need to have lot of knowledge to be successful and try to be better than your counterparts.
All the best!

Some of the good institutes are as follows:
MAAC, LISAA School of Design, Graphic and Design Institute.

There are many short term courses like Tally which you can do with Bachelor degree you can do diploma in taxation management foreign exchange. You can do diploma in import and export diploma in auditing is also there. These all courses are for one year and Tally is for 6 to 7 months.

Srimati Techno Institute | Hazra, Kolkata
Vision Institute of Professional Studies (VIPS - Kolkata) | Santoshpur, Kolkata
Kohinoor Technical Institute | Ultadanga, Kolkata
Exterior Interior Limited | Kalighat, Kolkata
WLC College India, Kolkata | Salt Lake City, Kolkata
https://www.shiksha.com/design/fashion-design/colleges/colleges-kolkata?uaf[]=credential&ts=5513598&rf=filters&ct[]=130&cr[]=11

There are lot of short management courses that you can pursue based on your graduation background and years of experience. NMIMS University offers a lot of similar courses.