Gathered a lot of info from the article linked in comment which interviewed a doctor from China :
1st Week : Mild symptoms
Fever (98.6% of cases), feebleness (69.6%), cough (59.4%), muscle pains (34.8%), difficulties breathing (31.2%). Less common symptoms : headaches, dizziness, stomach pain, diarrhea, nausea, vomiting.
75% will recover from here. For the other 25% that don't
2nd Week : Multiple organ failure
"But some patients who enter the second week will suddenly get worse. At this stage, people should go to the hospital. The elderly with underlying conditions may develop complications; some may need machine-assisted respiration. When the body's other organs start to fail, that's when it becomes severe, while those with strong immune systems see their symptoms decrease in severity at this stage and gradually recover. So the second week is what determines whether the illness becomes critical."
Many (20%) recover from here and live rest of the life with damaged organ. The last 5% enter the 3rd week.
3rd Week : Death
"The third week determines whether critical illness leads to death. Some in critical condition who receive treatment can raise their level of lymphocytes, a type of white blood cell, and see an improvement in their immune systems, and have been brought back, so to speak. But those whose lymphocyte numbers continue to decline, those whose immune systems are destroyed in the end, experience multiple organ failure and die.
For most, the illness is over in two weeks, whereas for those for whom the illness becomes severe, if they can survive three weeks, they're good. Those that can't will die in three weeks."
Final mortality rate is 4-5%.
Link to article in comment.