How do you pronounce "Congratulations" in Itaewon?

Hello! It's been a year since I came to Korea, I am currently studying Korean diligently in Itaewon. However, I recently learned the word 'congratulations' but I find the pronunciation a bit confusing. I wonder why it is pronounced as 'chu-ka'. At first, I thought it was 'chug-ha'. Maybe it's because I'm not familiar with consonant assimilation... Does anyone have a similar experience? I've tried using pronunciation correction apps and asked my friends, but I'm still confused. ㅠㅠ Could you please share any tips or recommend good apps that could help with pronunciation correction? I would be really grateful for any shared experiences!