How to use the curves adjustment
Open the image that you want to experiment with in your program.
You will want to make sure that it has varying shades, such as this image here.
Make sure that your layers dialog box is open.

Click on the small circular icon for your layer options. Choose curves...for the curve adjustment tool.

A girl glides down a slide. the girl

stands to her feet.

. a small boy wearing a black and red striped shirt

is sitting with a drum set and playing drums.

How to answer customer emails
Read the customer's email carefully.
Avoid the temptation to begin formulating a response before getting to the very last word in the correspondence. As you read the entire text, other insights may come to mind that will make it much easier to provide a truly constructive response.
Acknowledge the customer email as quickly as possible. Let customers immediately know you care for and plan on investigating their concerns, there is personnel responsible for such actions, and a solution will be reached.