YOU SAID:

hi my dog is called rex and he is very big and scary

INTO JAPANESE

こんにちは私の犬はレックスと彼は非常に大きくて怖い

BACK INTO ENGLISH

Hi my dog Rex and his very big, scary

INTO JAPANESE

こんにちは私の犬レックスおよび彼の非常に大きい、怖い

BACK INTO ENGLISH

Hi my dog Rex and his very big, scary