5800x3D still better than new 7000 series

I state that computer science is not my job … I am an owner of 3900x, because when I designed the PC it was considered the right CPU for a high-end machine. Now I hear wonders about this 5800x3d, but …

  1. why should it have such high performance if the clock speed compared to 3900x is more or less the same?
  2. The cost of the upgrade (considering that I would sell the old used cpu) is sustainable for me. But would I really notice any significant differences? (the system is RAM32Gb, 3700, 2560x1440 resolution)
  3. Would I have compatibility problems with MB and heatsink?

(and… don’t think I’m stupid. My job is teaching literature, for me MSFS is fun, if you don’t feel like answering just ignore my questions).