A resident permit under paragraph 25 (5) is issued first for three periods of six months validity. After the three periods (in total 18 months) have passed, the Ausländerbehörde can give them permits with longer validity (up to a maximum of 3 years). This is why your lawyer sent you paragraph 26. That paragraph details the rules about the lengths of different types of permit. If they have not reached the 18 months, then it is not possible for them to receive longer.
They can apply for permanent residency after 5 years of living with a residence permit in Germany (i.e. not any time spent with the green Ausweis Aufenthaltsgestattug or Duldung).