Deepali What happens if you try to save a second time; same error or does it save OK (eventually)?
Obviouly even if it does save it will likely be marked invalid given the unlinked items on the screenshot.
My advice on process design is not to try and build a big complex process in one go, but to start small and ensure the process saves and potentially works with just a few actions, and then go back and insert new additional features to expand on it.
To me your process seems to have too many work-in-progress areas.
Start small and build out is my advice!