If you genuinely lost your own MQ4 source code:
Searching for "ex4 to mq4 decompiler github 2021" usually leads to one of three scenarios:
Most GitHub tools are binary extractors, not true decompilers. They produce:
Basic usage (example from ex4_to_mq4.exe):
ex4_to_mq4.exe input.ex4 output.mq4
Or drag-and-drop EX4 onto the .exe.