Hi Kerstin,
This is a great question. Many people think those with liver condition such as fatty liver will have symptoms. This is quite the opposite! On the contrary, patients with chronic liver conditions like fatty liver do not have symptoms at all until very late stage where cirrhosis (liver hardening) occurs. Then they may feel fatigue. In more severe cases of liver cirrhosis from NAFLD (non-alcoholic fatty liver disease), patients may develop ascites (fluid collection in the abdomen), muscle wasting, or intestinal bleeding.

For the condition of fatty liver related to obesity - the best way is to reduce obesity and getting back to normal weight.

The lifestyle modification in this era I would say is to avoid ultra-processed foods, foods high in sugar content (such as sugar beverages, candies), avoid overeating, avoid eating too fast, regular exercises (at least 45 mins of cardiovascular workup about 2-3 times a week). 
Going outdoors, reduce screen time, avoid late dinner/supper, sleep well, avoid "stress-relief eating".
All these are difficult to achieve, so the treatment plan and lifestyle modification has to be tailored to the individual.

From time to time, drink and enjoy your coffee - coffee is actually good for fatty liver :)