YOU SAID:

I cant believe youve done this

INTO JAPANESE

私はあなたがこれをやったと信じていない

BACK INTO ENGLISH

I do not believe you did this

INTO JAPANESE

私はあなたがこれをしたとは思わない

BACK INTO ENGLISH

I do not think that you did this

INTO JAPANESE

私はあなたがこれをしたとは思わない

BACK INTO ENGLISH

I do not think that you did this