YOU SAID:

you must stretch good

INTO JAPANESE

しっかりストレッチをしなければなりません

BACK INTO ENGLISH

I have to stretch a lot

INTO JAPANESE

たくさんストレッチしなければなりません

BACK INTO ENGLISH

have to stretch a lot

INTO JAPANESE

たくさんストレッチしなければならない

BACK INTO ENGLISH

have to stretch a lot