YOU SAID:
get ready we have to leave soon
INTO JAPANESE
すぐに出発しなければなりません
BACK INTO ENGLISH
Have to leave immediately
INTO JAPANESE
すぐに出なければならない
BACK INTO ENGLISH
Must leave immediately
INTO JAPANESE
すぐに出発する必要があります
BACK INTO ENGLISH
Must depart immediately
INTO JAPANESE
すぐに出発する必要があります
BACK INTO ENGLISH
Must depart immediately
That didn't even make that much sense in English.