Thank you so much! On the QVL forthe mobo The Dims 1 and 2 are checked (not 4) for the mobo. So i assume it means i could get 2 kits of 2x8Gb ram. = 32Gb but not a kit of 4x8gb.
Not exactly. Just because the DIMMS in the 4 x aren't on the QVL, just means they haven't been tested with the mobo. It doesn't mean they won't work.
Whilst mixing two sets isn't the best idea, it should be okay. But you have a small risk they may not work. Ryzen used to be picky about ram, but the new B450's are great with almost all matched DIMMS. In this case, if you wanted 32gb, I'd suggest the 4 x kit, instead of 2 x 2 (8gb) sets. You could also go for 2 x 16gbs, but 4 x DIMMS is best for Ryzen and gets the best performance if they are all single ranked DIMMS, or 2 x 16gbs dual ranked DIMMS.