Bernat is terrible these days for PSG. No idea if he's supposed to be this bad, or if he just needs time to adapt to his new team, but he's bad defensively, and pretty useless with the ball since most of his crosses are bad.
Most PSG fans I know are begging for Kurzawa to be back. Which says a lot, considering he's been awful too. They've got Meunier and Alves as RB, a really solid starter and a good backup (even if Alves is injured, and aging), but they can't seem to find a LB decent enough. I guess it's a problem for several teams these days though.
Lyon won't sell him for cheap in january. They bought him for 6 millions, and he's performed very well since then. If they manage to reach UCL round of 16 (which is clearly doable), they'll have no intention of selling since it's going to be nearly impossible to find a player of the same quality. Plus, the competition for the top 3 in France is going to be tough, with Marseille and Lille (plus the occasionnal surprise), so they can't afford to weaken their team. I'd wager the only way to get him would be to pay something like 25 millions, for a player who's not going to be able to play in UCL for Barca (and who's still a bit inconsistent). And even like that, not sure it might work.