Hire a freelance MQL4 programmer on a platform like MQL5 Freelance. Provide them with a detailed description of the strategy or functionality you need. They can write clean, efficient, original code for you, which you will then own.
To understand why you cannot simply "convert" an EX4 file, you must understand what compilation means in the context of MetaTrader 4.
If you cannot contact the developer, you can hire a freelance MQL4 programmer through trusted platforms like MQL5.com or Upwork. Instead of asking them to decompile the file, ask them to . Attach the EX4 file to a demo chart.
There is currently no reliable, free, or public tool that can perfectly "reverse" a compiled file into readable source code.
MetaQuotes, the developer of MT4, has implemented strong anti-decompilation measures in the EX4 format, especially in newer versions (build 600 and above). These include:
These decompilers attempt to reverse the compilation process by: