When you wish to congratulate someone on certain occasion in Hindi you just have to say :
बधाई हो (badhaaee ho) means congratulations
you can say “बहुत बहुत बधाइयाँ (bahut bahut badhaaeeyaan)” which literally means “many many congratulations”
congratulation (noun)=बधाई (badhaaee)
congratulations(noun)= बधाईयाँ (bahaaeeyaan)
and to congratulate (verb) =बधाई देना (badhaaee dena)
मैने पीटर को बधाई दी (maine peter ko badhaaee dee) = I congratulated Peter.