Thank you ! = Shukriyaa / dhanyavaad = शुक्रीया / धन्यवाद Thank you very much ! = Bahut Shukriyaa / Bahut dhanyavaad = बहुत शुक्रीया / बहुत धन्यवाद

dhanyawaad-धन्यवाद shukriyaa-शुक्रिया thank u very much- bahut bahut dhanyawaad(in literature only i see 'bahut dhanyawaad' in general conversation we use bahut 2 times)