Answer to the point and try to give real life examples for concepts of OOPs Eg: Abstraction could be a switch board (the user only needs to know on and off and need not know the wiring, power consumption, etc) Also Try to answer in detail. Honestly tell them that you don't know what you don't know. Always remember to ask one question about the company. It is okay to ask the HR , "What do you like most about working here?" And it'll show that you are showing interest. The results usually take time to come. Make sure you send properly structured , Grammarly approved emails while enquiry.