I Weigh 98KG And I'm 6'5 Inches, And I'm 17, So How Much Should I Weigh?

As above, there is an "ideal" range.  However, these, you'll find, relate to BMI, in which case yes, you are SLIGHTLY "over weight"
But let me tell you, I'm 5'10 and 98kg myself and I'm VERY fit, I go to the gym and lift weights often as well as rock climb and practise several forms of martial arts, I'm also due to start with the RAF in a few months.

You know yourself if you are fat or fit, so if you're fit, keep doing what your doing, if you're fat.... Well, see above.

Iam 45kg and iam 17 is this weight Normal

Sounds right I'm the same height and weigh 95 kg a little lighter than you but not much I'm fit and muscular I lift weights so I don't need to worry about my weight if you're in the same boat then you don't either :) oh yeah and another thing don't listen to people who tell you that you're overweight because you're not. I'm very slim at 95 kg very tall people like us weigh a lot because we're bigger overall. And also my dad is the same height as us two he weighs 124 kg he's very solidly built from having years of a manual job he's not even overweight yet bmi says he is.