1. Do you have a link to a Lenovo B50 on sale? Also, we would need the full model name (B50-80 or B50-70 etc).
2. What country do you live in?
3. (Recommended) system requirements for Overwatch are an Intel i5 or AMD Phenom II CPU, 2GBs worth of VRAM - GTX660 or Radeon 7950. 6GBs of RAM and a 64-bit OS.
4. As for PCs in the €400 range, please name a few computer stores in your particular country - the Euro Zone covers a great many countries.