Can you use an Isofix base with this car seat?
If you mean the original car seat that is normally a part of the Kinderkraft Prime 3in1 set, then no, there's no Isofix base compatible with it. As a quite a cheap pram, that car seat was simply made very simple.
On the other hand, if one goes for the 2in1 Kinderkraft Prime and gets Maxi-Cosi/Cybex adapters with it - then buys a Maxi-Cosi, Cybex, Joie, Kiddy, Recaro, Nuna etc. car seat (all compatible with that kind of car seat attachment), then they could get an Isofix base to that particular car seat model. Not to the Kinderkraft one, though.