[thadajirajaras]

I think these all sentences are correct. -->
1) I said that I would go with you.
2)My idea is that we will go to play football tomorow.
3)I know him whose car is pink.
4)That word means "tiger" in English.
5)I see that box that is red inside your room.
6)I saw the man [who,that] was your cousin at the airport.

I think these all sentences may be incorrect. -->
1)I said to you that that I would go with you.
2)I have an idea that we will go to play football tomorow.
3)I know him that his car is pink.
4)I know that word in English which means "tiger".
5)I see that box inside your room that is red.
6)I saw the man at the airport [who,that] was your cousin.

Do I think correctly?