While doing ba graduation can I learn web development in 6-7 months and whatever time it take and earn money after that while doing graduat.

Yes you can do correspondence courses and diploma courses online for web development

Research online web design courses and programs. Find out what you can learn in these courses and what you'll need in order to participate in online learning to determine if it's right for you.

There are some apps which provide such courses like coursera, unacademy, khan academy, etc.

You can get these apps in playstore.

Web development courses are very useful for your future career. You can earn more money if you have knowledge of web designing.

Hope this helps!

Good luck!