Oh hun, you don’t need to gain 30 kilos, your BMI will be 25 which is where the overweight category starts but yea your current weight is too low. You should aim for 70-75 kilos as your weight actually 70 kilos will put you right at 21.5 which in the middle of the healthy BMI range.
As far as eating sweets, I love them too not only eating them but making them too. I guess we should try to eat smaller portions and try not to eat sweets all the time lol maybe once in a while