An asian teenager wearing a white shirt with black stripes is sitting on the steps with his face resting on his hand.
The teenager is sitting down to think for a bit.
The first sentence, while very detailed, does not say that to think is why he sat down.
Resting your face on your hands does not imply you are trying to think.
The sentence doesn't say why the teenager is sitting down. His face resting on his hand could mean he's upset or tired, not necessarily that he wants to think for a bit.