I have these 2 sentences:
1) "I tried to talk to my boss to explain how I felt about the job"
2) " I tried talking to my boss to explain how I felt about the job"
I know that in number 1 the person couldn't talk to the boss.
And I know that in number 2 the person talked to him.
I learned that the person didn't success.
But my question is ...How I know that the person in number 2 didn't success either?
It's not clear from the sentence itself. The context would make it clear.
The person tried -- that is, made an effort. Normally, if nothing else is said, we assume the person didn't succeed in the ultimate goal of making the boss understand, otherwise the sentence would have been "I talked to my boss..." Or it might have been: "I tried talking to my boss... and believe it or not, it worked!" Then the context makes it clear that the person did succeed.