I heard a buzz in the trans. i check the oil and missin 1 quart.
Do you mean you checked the transmission fluid? And you followed the procedure outlined in your Owner’s Manual? Then the logical next step is to add transmission fluid and see if the noise goes away. And since you have a leak somewhere you need to find out where and how bad it is. And if the noise doesn’t go away you need the services of a good independent transmission shop.
Problems w/Nissan auto-trans seem to get a lot of posts here. Suggest using the forum search feature, see what others have said, link upper right this page. It’s just the automatics for some reason, Nissan manual trans get very few posts.
Read about the CVT in your Murano.