Question - can you start a new game + while keeping your original game?

Probably a stupid question but I just finished the main story and currently grinding through to complete the side quests / Valkyrie’s etc… but I also would like to start a new game + but I don’t want to lose all the progress I’ve made with my original game. If I start a new game + can I still go back and complete missions from where I left off in my original game? Will it give me to game slot options?