Here "certain hope" stands for what the believer can confidently expect, that is, the things that God has promised to do for all believers. These things are spoken of as if they were physical objects that God was keeping in heaven for the believers to possess later. AT: "because you are certain that God, who is in heaven, will do the many good things that he has promised you" (See: [[rc://en/ta/man/translate/figs-metonymy]])
This is a generalization referring to the part of the world that they knew about. AT: "throughout the world" (See: [[rc://en/ta/man/translate/figs-hyperbole]])