how can I decided , what I can do better ( chemical engineering , mechanical engineering , medical )
Dear Aspirant,
Chemical engineering = chemistry + mathematics
Mechanical Engineering = Mathematics + Physics
Medical = Biology + Chemistry
Decide for the subjects you think you are comfortable with, and if you are not comfortable with mathematics then the choice is very simple, go for Medical without a second thought.
However, if you are good with mathematics then check for physics and if you are facing problems with physics, then I suggest you should go with medical again as it will be difficult to survive engineering without physics and maths.
And if you are comfortable with physics and mathematics, then see how much chemistry you like and then made the choice between chemical and mechanical engineering.
All the best.