If you purchased a key from a third-party site (like G2A or Eneba) and the game is locked to Russian or another language, the language lock is usually hardcoded inside a configuration file.
If the files are present but the game remains in another language, you can force English via the Windows Registry: and navigate to: Prototype 2 Pc English Language Pack
Locate any non-English language files (like Russian.p3d ) and back them up. Paste the English version of these files into the folder. If you purchased a key from a third-party