Question about Modern Standard Chinese (Mandarin) tones?

“that I should just listen to reporters to learn pronunciation. Is this true?”
I agree with it. Because just a short time ago, I didn’t know we Chines words Pinyin has sandhi in quite a few situations.

“He said in professional situations people do not use tone changes.”
May be, it’s true. But, what’s the meaning of “professional situations”? Sometimes we don’t follow the specialist’s advices.

The aim of speaking is to make someone “easily” understand. Sometimes, we just don’t like the “correct” pronunciation. And the real situation might be, if we don’t make some required changes, not only prevents others from understanding easily, sometimes it becomes weird.
The only rule I knew it a short time ago, I think you have already knew well, is when 3 tone + 3 tone, the first 3 tone is normally changed to 2 tone. Why? Because when you change the first 3 tone to 2 tone, it makes sound smooth. But, is the above rule an iron rule? No, I don’t think so. The above basic rule might still have some exceptions.

So, my opinion is, you don’t need to delve into the details. When you feel your speaking is smooth than before, that done.

Oh, I’m an English learner, I hope you can understand my poor writing.