1)
What is "Achen"?
1.
Rashi: In truth, [Radak - Hashem heard my Tefilah and took me out of Galus].
2)
Why does it say both "Shama" and "Hikshiv"?
1.
Malbim: He knew my matter (that I wanted to request), and hearkened to my Tefilah immediately when I began to pray [and accepted my Teshuvah and returned me to my kingship].