Finish an APP and Website Design almost done

I allocated and agreed to give a Freelancer the task of Developing my APP and Website.
It's now been over 8months and is unfinished.

The Freelancer had done a great job up to the end with delays and errors causing set backs. These set backs has resulted me in loosing thousands of potential earnings and clients.

The Freelancer has produced work that is incomplete, incorrect and now not working the way it should be.
The Freelancer is now refusing to fix and complete my project without me paying for it.
In summary... the Freelancer is holding my project at ransom even tho they are in brief of our deal.
I have paid this Freelancer for work up to date, meaning... once the milestone is completed. I pay.
To date I have paid thousands for the completed work.

I have drafts available for both APP and Website.
I have domains, I have a website.

What I need is someone to finish my APP and Website.
Is there someone who can help me?
Again, it's over 8months from a project that was supposed to be less than 3months.