I don't know how to get rid of these neck fat lines? (Photo)

It's best to begin by consulting with a surgeon in-person. The presence of banding down the front of the #neck, and, amount of excess skin and condition of your skin are among some factors which determine what treatments will best rejuvenate your neck . 
During your initial examination, your chin will be evaluated along with the neck and jawline. A weak #chin implies a lack of chin support for the skin along the neck line. In younger individuals a chin implant alone is usually all that is needed to improve the appearance of the neck. Subsequently, it will also improve the overall #balance of the face and can create the illusion of a smaller nose. As a stand-alone procedure, chin augmentation can be performed in the office under local #anesthesia. For individuals with signs of #aging in the neck, a chin implant added to one of the recommended procedures above, will provide optimal results.
If you are not a candidate at the time of your #consultation, your board certified plastic surgeon can recommend non-surgical alternatives to address your concern. Consulting with a board-certified plastic surgeon who specializes in #neck lift procedures is important to ensure you are receiving the best advice, care, and surgical experience possible.

Thank you for your question.  Unfortunately deep lines in the neck are very difficult to get rid of completely.  Treatment of the lines with a superficial Hyaluronic acid filler (such as Belotero) can make them look far less noticeable.Best wishes!Dr. Konstantin

This needs liposuction and thermi in combination with fillers to the actual lines themselves.  I suggest seeing an expert for a formal consultation.  These lines are genetic and won't be fully cured with anything but can be improved with a combination of options.  Dr. Emer.