Byju's is the best online learning resource. I have studied for a month using the byju's app and I got fully prepared for my board examination.
This app is awesome , it cleared all my doubts in science and mathematics. There are teachers for each subject. They let us understand all the things with clarity. They give a full explanation for every single topic and get very deep inside it. A test is also taken after the explanation of each topic. This app is best for class 9 to 12.
The content of the app is in English and if you are finding any source to learn things clearly , then you should give it a try.