Quiet
な adjective
This is the な adjective form of quiet, which is kind of just like the noun, anyways. What is the adjective version of quiet? It's also quiet.
しずか
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: You need to be quiet. She's (しず) being nice and quiet, unlike you!
今日は静かですね。
It is quiet today, isn't it?
すみませんが、もう少し静かにしていただけますか？
Excuse me, could you please be a little more quiet?
コウイチとビエトを乗せて、そのタクシーは静かに動き出した。
With Koichi and Viet on board, the cab quietly started to move.