You can't do anything 'bout it. get someone to fix it or buy a new game.
Maybe something is wrong with your DS, it hasn't happened to me or any of my friends.
You held L and R too long! Turn off your D.S and try again. If that doesn't work you have too much cheats on or too many fake cheats
the fifth gym on Pokemon diamond is the one in herthome city,
in canalave city
its for decoration
eterna city
Eterna City I think
Synshrone city is not a real city in Pokemon Diamond.
Blackthorne city is not in Pokemon Diamond but in Pokemon Heart Gold/Soul Silver
Fortree City is a location exclusive to Pokemon Ruby, Sapphire and Emerald. This means it is impossible to visit Fortree City on Pokemon Diamond.
the fifth gym on Pokemon diamond is the one in herthome city,
The first gym in Pokemon diamond is in Oreburgh City
south of hearthome city
Pastoria City.
its not in a city its on a route
There is no such thing as turtwig city
he is in Eterna city.
cancalave city
its in pastoria city