1) By the time I joined AMX, I had started feeling unwell.
Please check my sentence.
Note the addition of a comma above. You can also say "By the time I joined AMX, I was already [feeling] unwell."
Bear in mind that I don't know what "AMX" is so I can't say if the sentence makes sense.
I had worked that out for myself! As long as the company has some relevance to your feeling unwell, it's OK.
Sorry for this post but can I also say "By the time I heard his accent I had know he was an American"?
No. "By the time I heard his accent, I already knew he was American".
'By' in 'by the time' means 'before or not later than' according to definition #8 at https://www.ldoceonline.com/dictionary/by.
I think 'When' can be used instead of 'By the time' there.
Okay, thank you, but let me tell you one about an incident.
I got a call from a consultant. He wanted me to come for an interview but I was a bit reluctant.
1) By the time we finished talking, he had agreed to me/my [STRIKE]to come[/STRIKE] coming for an interview.
2) By the time I finished conversation with him I had understood that I had been persuaded by him to come for an interview by him. So unnatural and impossible that I'm not even going to start trying to correct it. No one would say anything like this.
Are these correct?
After talking with him, I agreed to go there to be interviewed by him.2) By the time I finished conversation with him I had understood that I had been persuaded by him to come for an interview by him.
I think 'When' can be used instead of 'By the time' there.
Still a very unlikely utterance, Matthew.After talking with him, I agreed to go there to be interviewed by him.
Sorry for this post but can I also say "By the time I heard his accent I had know he was an American"?
Why can't we use "Present perfect" here? In the previous sentence it was acceptable. What is the reason behind this? What is the proper way of using this structure?
See above.