I have just checked your page:
1) Space between WOWSlider and menu.
You use "Crystal" template. This template has a bottom shadow. So, 39px is added under image for shadow. In other case it will overlap a content below, that's not look good. You can use "Remove frame and shadow" option at Gallery->Properties->General tab or use another template without bottom shadow.
Also, your main content indents from header for 15px. Please see:
2) Image quality.
I don't know about quality of your original images, but images on your server are really bad:
Make sure that your original images have a good quality and you set high quality (90+) for images at Gallery->Properties->Images tab.
If problem will persist, please send us your original images, WOWSlider project file (.wowsl) and provide us information about WOWSlider version and your OS.
3) "Delay between slides" and "Effect duration"
"Delay between slides" is time of image displaying. If you set "Delay between slides" 2,0s, it means that each image will be displayed during 2 seconds.
"Effect duration" is time for switching between images. Higher value makes the transition from one image to another more slowly and smoothly.