Hi Nima0041,
While it is true you do not need to known C++ to use the engine and develop games, this may not be true for some things you are looking to achieve as your game grows in complexity. We are always adding functionality to our visual scripting with Blueprints but this may not cover everything you may need.
With our content examples on our Marketplace there are some game examples that exclusively use Blueprints with no programming code used at all!
If you have any questions feel free to ask!
Thank you!