Peer-reviewing process of an article I am doing a PhD and I have submitted an article to be peer-reviewed 9 months ago to a certain journal. I haven't got any response yet from the journal, their server indicates the "Under review" status. 
The problem is, I cannot wait more longer since the acceptance of the article is a requirement to validate my PhD.

Do you think I can stop the reviewing process and send it to another journal?
What if I sent it to another journal at the same time?
Or, would the reviewing process speeds up if, e.g. I pay for the open access?

EDIT:

I forgot to mention that the status cited above stipulates that:


  At least one Reviewer has accepted to review the submisѕion, however the required number of reviews for the submisѕion have not yet been received.


I have provided 5 names for the peer-reviewing process of my article, and mentioned that 1 potential reviewer from another university should not review it (because of competitive reasons).
"Under review" for nine months is normal in some disciplines


  Do you think I can stop the reviewing process and send it to another
  journal?


No. This will most likely delay the process even further.


  What if I sent it to another journal at the same time? 


No. This is (most likely) prohibited.


  Or, would the reviewing process speeds up if, e.g. I pay for the open access?


No. Open access is entirely independent of the reviewing process. The former is handled by the publisher, the latter is handled by your peers.