YOU SAID:

i have to go and find a toilet of my aunty will have pee in her cup of tea.

INTO JAPANESE

叔母のトイレに行ってお茶を飲まないといけない。

BACK INTO ENGLISH

I have to go to my aunt's toilet and have some tea.

INTO JAPANESE

叔母のトイレに行ってお茶を飲まなければならない。

BACK INTO ENGLISH

I have to go to my aunt's bathroom and have some tea.

INTO JAPANESE

叔母のトイレに行ってお茶を飲まなければならない。

BACK INTO ENGLISH

I have to go to my aunt's bathroom and have some tea.