How can I earn well after completing 12th with science in less time?

You should learn some skills from udacity. Com, udemy. Com etc. And after then, you can try in freelancer. Com, you have also option to earn money from youtube. There are lots of way but hard and continuous work is important. Make sure you are doing right and don't share any kind of information with

After Normal course, there are no job at all, you have to do a skill course.