先生、父の手術の成功率はどれくらいですか。心配でなりません。って英語でなんて言うの？

▪ Hi Doctor, what are the chances for a successful surgery for my father?
I feel worried.

▪ Doctor, will my father's surgery be 100'% successful?
I am very worried.

>"chances" is asking the doctor for a percentage answer, 50'% positive 50'% negative or 80'% positive 20'% negative.
>"worried" is showing concern about the surgery.
>"100'% successful" means that surgery will be completely successful.

You can also ask:
-Doctor, what are the disadvantages of the surgery?
This is asking what will or can be the downfall after the surgery.

Hope this helps.

These are informal statements used to find out how the surgery will go. Is it likely to go well and what will the result be afterwards?

"What is the success rate?" This is the most common phrase that I've heard when it comes to asking if the chances of success (outcome) are high or low for surgery.
"Is the risk high or low?" This is a way to ask and see if there are any things (risks) that can happen during the surgery that will determine if it is successful (a good outcome) or not.

When addressing a doctor you simply call them 'dcotor' if something works then it is said to be a success or successful if you are concerned or anxious/nervous then you are said to be worried

"I'm very worried for my father, whats the likelihood of a successful surgery?" the expression 'likelihood' is used frequently when phrasing a sentence around 'how likely or what are the possibilities'
"what are the chances" is another phrase in which its describing the possibilities of such event.