Manual is just that, you manually choose a focal point by touching the area of the image you want to focus on, multi will focus on multiple areas, and attempt to get the whole image in focus, and center uses the center of the image as the main focal point. Grainy images are usually due to the ISO setting in pro mode, general rule of thumb is the darker the setting, the higher the ISO setting needs to be. Downside of this is the Higher the ISO, the resulting image will be more grainy. Soft-Focus is usually an aperature issue. It is a fine balance (and somewhat of a science) familiar to most professional photographers - hence the label "pro" mode. There is no single setting that will work best in "pro" mode for all settings (background, lighting, distance, moving objects, sports, etc...) each of those situations will require different settings in "pro" mode to achieve the highest quality image you desire.
If you provide an example of the photo setting, I could better guide you on how to set your camera in "pro" mode. Im assuming since you mentioned grainy images, you are trying to take photos in low light situations. You can try adjusting the iso until you achieve your desired result. As far as the soft-focus, thats probably due to the focus mode being incorrect for the photo you desire.
