Hello iriis
Yes, that should be possible. With other Samsung Dual SIM smartphones, this works without any problems from my own experience.
They are both nano SIM card slots and as far as I know, both cards cannot be registered in the same (4G) network at the same time (here I am talking about two CH network SIM cards). This means, for example, 1st SIM in the 4G network (e.g. Sunrise/CH card) and 2nd SIM in the 3G network. The "Main" SIM can be changed in the settings - at least on other Samsung Dual SIM smartphones. Both SIM cards are "active" and accessible at the same time.