acer nitro 5 ram slot

My Laptop is Acer Nitro 5 - AN515-57, and comes only with 1 stick of 8GB DDR4- maybe X16 memory with 3209Mhz speed. slot demo cosmic cash Now which RAM should i buy for it I have seen most of ram upgrade videos but still not getting it, cuz when most of them upgrade their ram in dual channel, they get clock speeds clocked at 2933Mhz, but supported is 3200Mhz