Changing positive statement to nagative statement using not

Yes at that time you need to use the opposites. For example:

The man is rich

The man is not poor

The most common way of turning a positive statement into a negative statement in English is to add the word not (or the contracted form -n't). In a declarative sentence, the word not is usually placed after a helping verb (such as a form of do, have, or be). Similarly, in less formal writing, the contraction -n't may be added to the helping verb.

Example: The police concluded that the security system had not been working properly.

Explanation:

me

explanation: