magdem, I understand how overwhelming this is for you. I can try to clarify a couple of things to add to what your doctors have said that might help a bit.
By definition a prognosis can only be based on what has happened in the past and to other people. So any timeline any doctor gives you is always and only based on an average of what has been the actual result for other people in the past. The bottom line is that we are all going to die from something and some point. You could die tomorrow or you could die in 50 years. So, IMO, dwelling on a statistical prognosis, is a waste of precious time.
I would recommend getting a clarification from your surgeon regarding the lesions being to small to biopsy. If they can be identify from a CT scan or MRI, they can certainly be removed for a biopsy. There may well be other very valid reasons not to do a biopsy, but I doubt that a mass being too small to remove would be one of them.
Stage 4 cancers are rarely curable but they can often be treated and the cancer managed as a chronic disease, similar to heart disease, diabetes, or hypertension. Doing so often involves some degree of quality of life reduction as does declining treatment.. What route to take will be entirely your choice, but my recommendation is to not drive yourself nuts trying to make that choice until after you have all the relevant information you need to order to made an informed decision..