If you say "belki" there is a chance here. Maybe it can be or not. Belki sınavı kazanırım. (maybe ı pass the exam but maybe ı dont) Galiba sınavı kazanacağım. (My exam was good, I think I solved most of the problems correctly) Galiba annem evde. (My mother's car is here and I think my mother is home) Annem belki evdedir. (I cannot be sure whether she is home or not, but she can be at home) There is also a chance when we say "galiba" but the difference is that we have some clues which make us think like that.

There is a inference in "Galiba". -- It should be, I have some explanations of observations. -- There is a chance in "Belki". -- I don't know, It may be, or may not be --

comment of only is correct :)

cooment of only is correct

belki= maybe galiba= as far as I know