[Question] how change a dll?

Hello,

i have a dll ( hack for a game ) how can i open it and change somthing else?
which programm i need?

I hope anyone can help me :)

Kannst zum Beispiel OllyDbg oder IDA nehmen. Assembler-Kenntnisse nicht im Lieferumfang enthalten!

you cannot "change" the source code, if you mean that.
you can only change the code in machine language with a disassembler/debugger/patcher, but you need reverese engineering experience for this