First we have to see the differences of transitive and
intransitive verbs. The transitive verb has a direct
object; it transfers its action upon an object. The
intransitive verb does not have an object, actually
can't have a direct object. Have look at these phrases:
What kind of direct object would you like to add?
I swim my house. You swim bread and butter.
You see the verb to swim actually doesn't need and doesn't
use an object. It is an intransitive verb.
You see? And here is the first rule: intransitive
verbs (those without the direct object) like
to swim, to return, to arrive etc. form their negation
always with nicht.
= I do not
Ich laufe nicht.
= I do not walk.
Das Flugzeug fliegt
= The plane does not