Endgame Questions

For anyone who’s played a lot of the endgame, I’m curious if you’ve got answers to some questions.

1. Character level maxes out at 50 but mission levels go up to 80. How do you deal with this? Is it just a matter of upgrading your weapon and optimizing your loadout?

2. What’s the best way to get five-star weapons? So far I’ve only acquired like four of them and none of them are really my preferred weapon type.