No, you don't have to, but it definitely helps. If there is no documentation and knowledge sharing in your own language, then you will be constrained to the most basic level of programing. You can't find, invent, or deduce everything that thousands others have created and deployed for decades. Countries like Russia and China have big enough communities that they can maintain knowledge base that is sufficiently large to serve most of the needs of their communities, but even then knowing english helps to not reinvent the wheel at any single step.