Yeah, what I did is wrong like you explaned it before. I just diden't see it then. what I can do is preserve that memory, but that isen't make me a 2D array with a variable size.
So what what I have learned today is, take both sizes fix... most easy solution and handle overload or I do one variable size for the Filename or I one variable size of number of files. It's a choose I have to made depending on from what I have the most to save so much memory I can for the mcu.
PS: I will run this at startup to minimize memory issues. And as we discussed before with the risk when I take a pointer that the memorie could cause strange phenomenons like malloc error in the stack.