"덕분에 이렇게 행복한데 질릴 리가 있나요" = I am so happy thanks to it/you/them, so how could I get tired of it. (덕분에 is referring to somethong just mentioned) X 덕분에 = thanks to X. 질리다 = get tired/sick of something. X-ㄹ 리가 있나요? = X-ㄹ 리가 없어요 = it is not likely/possible to be X.

Hello