to negotiate or not to negotiate. That is the question

Hi all,
The end of the league is coming soon, and I plan to reconstruct my team for the next year.
I am in a dilemma:
1. I have a fast trainer but he's 4*, so no matter how much I train him, he won't reach the near 6* in a season. So I think I should sell him since he is worth a lot. Should I sell him now near the 5* or shall I want for next season's negotiations? Moreover, the players lose market value each year and that's something I need to consider.
2. Is the negotiations market profitable? I mean, do you get a lot offers? Should I count on it? Will I make tokens of it?
3.Do players play worst each year? I have players who are not expensive but they play good. I consider selling them this year instead of loosing their value next year. Considering they won't be good next year. Do you have experience with 3* players who play good as last year when they were 4* ?
4. Is it worth selling them near the end of the season with high value or next season with another star and less value? I want them to get into bidding wars so I would gain their value at least, or even more.
5. How do you scout players on negotiations? Do you look for statistics? Do you get bids from managers outside your league?
Thanks

i go with neg list as you can tokens too, i,v just sold a 3star 1 token player for 5 tokens :)

edit; i now have 2115 tokens and made most of that from neg list the last 8 months as my transfer market was a donkey but thank God it`s back :)