Mate just practice, practice and practice. If you happen to find concepts difficult, ask your teacher or if that still doesn't help, research on the internet. Understanding the concepts in topics such as probability and motion, can get confusing, so it's important that before you start practicing questions, that you understand the basic theory behind everything - again, to gain an even better understanding of the content, research them on the internet. Once you get the gist of the content, see how it's applied in real life - that should give a better understanding. Hope this helps.