YOU SAID:

my feet are warm because i have a dog sitting on them

INTO JAPANESE

犬が座っているので足が暖かいです

BACK INTO ENGLISH

My legs are warm because my dog is sitting there.

INTO JAPANESE

犬がそこに座っているので足が暖かいです。

BACK INTO ENGLISH

My legs are warm because the dog is sitting there.

INTO JAPANESE

犬が座っているので足が暖かいです。

BACK INTO ENGLISH

My dog's legs are warm because I'm sitting there.

INTO JAPANESE

私がそこに座っているので、犬の足は暖かいです。

BACK INTO ENGLISH

The dog's paws are warm as I sit there.

INTO JAPANESE

私がそこに座っていると、犬の足が暖かいです。

BACK INTO ENGLISH

The dog's paws are warm as I sit there.