Read this if you're having problem's with your G/S/C/ save file

By Wikipedia
A common problem found in the second generation of games is a problem with the internal battery after roughly six years. The internal battery is located inside of the cartridge which allows the game to save the user's progress. Many people have reported that their games no longer save due to this problem. It is possible to fix this, but the cartridge must be opened and the battery must be taken out, and a new battery must be soldered in. The battery model is similar to model CR2025, and can be purchased at any electronics store. However, the internal battery has small conductive tabs spot-welded to its exterior, and are difficult to remove from the original battery. Although if the parabler secondry battery can be obtained by further dismantling of the game this will automatically fix the problem if removed and then the rest of the game is put back together.