Adjective or Adverb ?

The adjective is only correct if used as such. For example, "He stood, motionless, and watched the parade."

You must use an adverb in the following sentences:

I talked seriously to the teacher.
The boy plays happily in the garden.
She ate her meal hurriedly.

Ask your teacher about this:

"She painted the picture beautifully". Does that mean she painted with a flourish and dramatic movements, like a dancer would "dance beautifully"? Or does it means the resulting picture is beautiful. I would think that in most cases we are talking about the results, so I would say "She painted the picture beautiful".

Now your teacher will say sorry, you should say "She painted the picture beautifully" regardless of logic. So then ask the teacher about this sentence: "She painted the barn redly". The barn is now a beautiful red!