Doncaster have made forward Dany N'Guessan their sixth summer signing.
Tottenham have confirmed that Romanian defender Vlad Chiriches has completed a move to Napoli.
The Norwegian boss is keen to secure the services of the central defender, who sees his current deal expire at the end of the season.
Berra has only missed one league game for the Molineux club this term, and Solbakken believes he has seen real improvements in his performances.
The Wolves boss told the Shropshire Star: "We're in talks with him, so we will see where it ends.
"Berra has been outstanding. He's gradually getting better and better.
"He's not Franz Beckenbauer, but he's improved tremendously. I think he had a tendency to make excuses for everything, but he's grown mentally.
"I think he had to sort out his head in terms of being tougher with himself."