1. I just realized that 'place in the sun' is an idiom.
Can anyone explain why the idiom has such a meaning?
place in the sun (source: Cambridge)
an advantageous position:
He certainly earned his place in the sun.
I don't know what the climate is like where you're from, Nefertiti, but when it's minus 40 degrees C or F [they're equal at that point], a place in the sun is indeed an advantageous position.
2. Does 'move on' mean to keep on or to continue?
It's similar to both.
3. Does 'before my life is done' mean before my life is finished or before I die Is it a common usage?
"before my life is finished or before I die" mean the same thing. It's quite common.
4. ' You know when times are bad And you're feeling sad' What does 'times' mean? apparently, it's countable. Is it OK to say, "times are good and you're feeling great"?
Those times when things are not going well for you. Yes, you can have 'times when things are going great and times when things are going terribly.
Thanks in advance.