I think "that is not entirely true" should be accepted as well

The suggested solution "That is not eactly true." is obviously incorrect.

I would suggest: "That is not quite true."

''That'' is correct but ''This'' is wrong...

That is not correct or exact does not carry the same meaning as that is not true, nicht wahr ?

I think "that is not fully true" should also be accepted.

I wich "that is not exactly right" would also be right. couldn't decide if I should use true or right... since I believe on the contectst what you would like to use, or how you choose to express yourself. In swedish we have a word "stämma" which I believe is equal to "stimmt" but we also have a word for right and true, so If you want to say "stämma" you have to choose which word to use...