YOU SAID:

i am going to run so dang fast

INTO JAPANESE

私はとても速く走るつもりです

BACK INTO ENGLISH

i'm gonna run so fast

INTO JAPANESE

すごく速く走れるよ

BACK INTO ENGLISH

I can run very fast

INTO JAPANESE

私はとても速く走ることができます

BACK INTO ENGLISH

i can run very fast

INTO JAPANESE

私はとても速く走ることができます

BACK INTO ENGLISH

i can run very fast