Wordpress is down : look like a hack

Hello,

We're experiencing issues with our Wordpress website since Nov. 4th (today). 
The site has been showing signs of slowing down in the past week, and today I was informed that it was entirely down (Critical error message on Wordpress, see picture attached).  
When I managed to log in the admin page, I discovered a serie of ''customer reviews''; seems like the issue here, like a hack (See picture of customer ''reviews'' attached).  
Since I have no control on the tech side of the website (I can only edit the content), what can I do ?
Is it salvageable or do we need to build a new website? 
I was said that wordpress is not the best regarding security... 

Thank you in advance for your help 



Émilie for Club Toastmasters YWCA Québec (Number: 01377570, 61, Area I92)
toastmasters-ywcaquebec.ca/

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