Hello, in order to help you, as the colleague has commented, you must provide more information, for example the game you are using, screenshots, the size of the save and, if possible, the save file as well.
Hello, there are several options, I recommend that you watch the videos and decide. There are three that I know of:
1. Use a DS Lite.
2. GB Operator (Epilogue)
3. GBxCart RW
Since it is a hackrom I don't think it can help you, maybe the way of saving the sav changed compared to the original and when editing it you corrupted it. I'm sorry.
Good afternoon, firstly, there is no need to write everything in capital letters and secondly, attach the save file that is giving you the problem. With such generic information and without the file, I don't think anyone can help you.