Correct. The amplitude is $\displaystyle{\left|-{3}\right|}={3}\usepackage{cmbright}\Huge\$ . This tells you that the y-coordinate of the high point is 3.

The period of this function is $\displaystyle\frac{{{2}\pi}}{{\frac{\pi}{{2}}}}=\frac{{{2}\pi}}{{1}}\cdot\frac{{2}}{\pi}=\frac{{{4}\pi}}{\pi}={4}\usepackage{cmbright}\Huge\$ .

On the interval $\displaystyle{\left[-{2},{0}\right]}\usepackage{cmbright}\Huge\$ the graph will have half of a cycle. If you graphed $\displaystyle{y}={3}{\sin{{\left(\frac{\pi}{{2}}{x}\right)}}}\usepackage{cmbright}\Huge\$ , there would be a valley on this interval. Because of the negative sign in front of $\displaystyle{y}=-{3}{\sin{{\left(\frac{\pi}{{2}}{x}\right)}}}\usepackage{cmbright}\Huge\$ , the graph has a hill on $\displaystyle{\left[-{2},{0}\right]}\usepackage{cmbright}\Huge\$ (and valleys to the left and right). The high point is in the middle of the hill, so the x-coordinate is $\displaystyle-{1}\usepackage{cmbright}\Huge\$ .