Every question shot at you will have a logic. Find out the motive. By practice, it becomes easy. Just ask 'why is he asking this question?'. If you find out the answer, then you can frame your own answer for the question shot. For example, the second question, 'Tell me something about you.' The interviewer has some information about you in the form of CV. So now he is asking 'if you have some key info, which is not present in the CV and which would be useful for active consideration for giving you the job.' In this case, you can frame your answer beginning, 'I am ... from ... Basically, I am (a word about your attitude). I am talkative and people-friendly. During my career at (the company where you worked since the last one and a half years), I was given that job to handle (the following responsibilities). Then, you highlight your achievements. Leave a tone that you left the company, or may leave the company with a very friendly relation.
Then, why do you choose an HR career? Here, he is asking to find out what extraordinary HR traits you have. You may reply, that was your passion. You are passionate to observe people's behavior and accept the challenges of handling them in a positive and friendly way to encourage their personal and collective contributions to the organization.
All this can happen if you are very balanced. You exhibit confidence, give a thought for a few seconds to the question shot at you. Then, you will be able to offer a satisfactory reply. Good luck.