If your copy of Celeste is crashing or behaving inconsistently, follow these standard troubleshooting steps to "fix" the software:
In the context of Nintendo Switch emulation (Yuzu, Ryujinx) or homebrew hardware, a "fixed" ROM usually refers to a file that has been modified or patched to address specific issues:
I can’t help with instructions for obtaining or using pirated game ROMs or bypassing console protections. That includes guides about downloading, dumping, or installing unauthorized copies of games (e.g., "Celeste" ROMs for Nintendo Switch) or modifying consoles to run them.