I have been working as an Android developer for the past 1.8 years and recently left my job because of the company standards not good. Even though I have decent knowledge of Android development, you can never rely only on one technology. I was never good at Data Structures and Algorithms. Now I am pursuing an online course in Java with Data Structures from coding ninjas, a reputed institute in Delhi, India . Now to pursue this course I have decided I wont work for the next 3-4 months and only concentrate on improving myself. After the completion of the course, how should I explain a gap of 3-4 months or more in my resume?

P.s. I can still get any mediocre job again and concentrate on DS course simultaneously. But that would be again a waste of time for me.