Extending visit visa.

Good day everyone im so thankful i found a firum like this. Me and my boyfriend is so confuse coz we want to make my stay longer coz he will be having an operation on march 9 and my visa is just goid for 90 days and it will be expire on 18th of march. Im hoping i could stay here with him until his recovery. Now we read about how to extend my visa and it says that i need to apply in Migration agency but we are confuse where catogery should i fall in applying. Should i just apply for another 90 days extention or apply for visitor's permit because we read that they have different form to filled up and submit. I want to stay with him for maximum days im allowed. We are not that young anymore im 50 years of age and he is 58 being together make us both stronger. I will highly appreciate if some one can give me a good advice. Thank you in advance.