YOU SAID:

I've never seen a snake like this before

INTO JAPANESE

私は前にこれのようなヘビを見たことがないです。

BACK INTO ENGLISH

It's like before I never saw the snake.

INTO JAPANESE

ヘビを見たことがない前に、それはようです。

BACK INTO ENGLISH

Have never seen a snake before, it seems.

INTO JAPANESE

見たことがない前に、蛇をです。