what will happen after that?

i had brain tumor 3 months ago,i undergo surgery to remove it,chemotherapy and radiotherapy everything has gone ok
i finished my treatment 2 weeks ago
am 58years old female,i had GBM of fourth grade,which is as i know it is the hardest one
my question is what is the possibility of being servived??i know the possibility is very low,but i feel myself very active,my health is better and i feel stronger and stronger
no pain, no headaches and i started to have a normal life
the other question is that how could i know that my condition is being stable,or the disease is progressed
is their any signs or symptoms indicate what is my condition other than doing mri