partial suction and refilling of coolant

Hi, with my car the coolant would have to be changed soon. As far as I know, the medium also has additives that should prevent e.g. rust from being created inside. Does the entire system have to be emptied, rinsed and refilled, or can I just suck off so much of the container until it is empty and simply fill in fresh coolant? Would that be enough, or should one rather let off completely? I would have to go to the workshop for this, but I would have to have my car almost every day ready to drive (career). So in short: Is it only enough to empty the container and fill funds again up to Max., or yet workshop and completely change? Does it also bring something if I just do the suction and refill method, or could it then happen that it starts to rust at some point? Would be grateful for useful answers (don’t know me about the matter really well)