I'm absolutely sure you can make it!这样比较象外国人的说法。不是字面直译
I believe you can definitely
表达的感情稍强烈,要用到副词
I trust you!
I'm sure you can make it!
I believe you can!
比较口语化的:Sure, you can!
我晕!!在线翻译都能翻译出来!
I believe that you can do it!
I believe you can!
I think you can make it!
很灵活的,呵呵,不知道可否说一下您的context(语境)?