Okay so my uncle just gave me his old Nikon D850 because he upgraded to something else and I am completely lost like seriously i dont even know what I am doing with this thing. It looks so fancy and heavy and there are way too many buttons but I really want to take good pictures of people.

My sisters wedding is coming up in like three weeks in Chicago and she expects me to be the photographer now that I have this huge camera but i honestly dont know what lens to use to make her look good. I want that blurry background look everyone has but when I take pictures now everything looks flat and kind of boring. I have maybe 800 or 1000 dollars to spend if I really stretch it but cheaper is better because I still need to buy a memory card and a bag and stuff. I keep seeing people talk about prime lenses and mm numbers but it makes my head spin and I dont want to buy the wrong thing and ruin her big day.

Sorry if this is a total amateur question but is there like one specific lens that every d850 owner uses for portraits in 2024 that isn't too hard for a total beginner to figure out? I just need something that works...