Cooling water boils- Workshop means cylinder head gasket R19

hi, I don’t understand anything about cars, my parents drive a 1993 Renault 19 and have actually already renovated a lot about the car: clutch disc, brake disc, end stage, then there was something about the carburettor (the line that hangs on the gas pedal, I think or so), suspension springs, both exhaust pots renewed. allidngs we have a problem, for some time the cool water is brown and in summer already overcooked, it was called that at r19 nothing unusual, have from time to time cool water now the engine temperature indicator is already after 3-5 minutes on MAXIMAL!!!!! also the internal ventilation (warm scent for passengers my) remains cold !, naturally we are to the workshop, first of all it was fixed that the fan (this propeller) did not work anymore, the switch was changed and then the also went at least test time, but as cool water replenished wu rde immediately boiled the cooling water, bubbling. then workshopman said that it was probably cylinder head gasket and that the repair of the old car might not be worth it any more. so he said it would cost between 500-600 euros (small free workshop, which used to have already patched the exhaust box beer etc. so actually trust person). do you mean my description and the diagnosis cylinder head gasket fits together? means your price 500-600 is ok? thinks you e so my parents and I hardly know each other with cars and would fear with a used car purchase that the car then very quickly has exactly the errors that we have fixed all the years at the r19 so exhaust, brake discs, clutch discs etc. besides, my father thinks it would be nonsense to buy an equally old used car where we don’t know what will be missing soon. think but repair of say times 600 euro is more than the rest of our car, on the other hand no money there to buy any new car. would like to hear comments and TAUSEND DANK!