What does "Reviews Completed" status mean in Springer?
It's waiting for the editor to read the reviews and make a decision. This could mean one of the following: 'reject', 'submit as new', 'major revision, 'minor revision' or 'accept' (Depending on the journal, options may change). 

Any decision above 'major revision' is good, meaning you get a chance to improve the paper and hopefully get to full accept.  Of course the paper can still be rejected at any stage until it is fully accepted.  

Best of luck!