I gain weight surprisingly in a few week, from 59 to 64...how come? I eat healthy like every day (I'm professional cyclist)

See DOC/Nutritionist. Weight balance depends on many factors- basal metabolism rate, balance between calorie intake & expenditure, level of physical activity, genetic predisposition, & hormonal balance especially thyroid hormone. You should see a DOC, check for hypothyroidism or other medical conditions that may affect your weight. Also talk to a nutritionist to review calorie intake. Good Luck!
Several things. Are you sure you haven't gained muscle .. though that would be a significant increase over several weeks. Alternatively have you recently decreased your training regimen. Otherwise it's difficult to suggest a cause without having a better understanding of any other symptoms during this time, how your clothing fit has changed, etc.
Probably Ok, But... I'm assuming that you are talking about weight gain in kg, rather than lbs. A weight gain of 5 kg (approximately 11 lbs) over a week does seem fairly sudden, unless you have significantly changed your eating habits, become severely constipated, or over-hydrated for several days. It could also occur with a significant change in exercise, such as not cycling for a week. Talk with your doctor...
? change in exercise. If you are eating healthy and have not changed your diet, then consider whether you have changed your exercise plan. A decrease in exercise frequency or intensity can result in too large a calorie intake for your slow down in exercise. IF no change in exercise intensity or diet then discuss checking your thyroid functions with your MD. Hypo thyroidsim can cause unexpected wt gain.