how much important is MSBI for a web developer/freelancer?

First of all, I don't think anyone can be good in one month. Sometimes it takes 6 months or more to become just good enough. Doing real projects will help.

You need to find out what your goal is? If the goal is to find a better job that pays well, its probably better to do some research what kind of jobs are in your city/area. I'm sure after COVID, many company would want to see you in person.

Front-end developer is probably a better choice than MSBI. I don't think there are too many jobs on BI unless you already have done your research.

Front end on the other hand (HTML, JavaScript, CSS) combined with Angular or React or even React Native is probably a better bet.

Good luck!