YOU SAID:

i have, in fact, seen a rather fast chicken, not one, but many

INTO JAPANESE

私は実際に、1匹ではなく、かなり速い鶏を見ましたが、

BACK INTO ENGLISH

I actually saw a rather fast chicken instead of one,

INTO JAPANESE

私は実際に1匹ではなくかなり速い鶏を見ました、

BACK INTO ENGLISH

I actually saw a rather fast chicken instead of one,