Speaking punjabi? loss of culture? don't know mother tongue?

am a 16 year old sikh girl living in England and although my mother and father can both speak punjubi fluently as were born and grew up in India, neither me or my siblings can. This really gets me down when i see relatives and tey try to speak Punjabi to me and i just don't know how to respond. I really feel that i should know the language and be able to speak to the rest of my family, who all are able to speak Punjabi well. Is there anything you could recommend for me to do< maybe a course at University could help me as i am planning to do an A-level in Spanish. Any suggestions would be greatly appreciated.Thank You