Requesting for some help with my network setup.  I have 2 identical networks in 2 buildings next to each other.  Each have their own ISP (fixed IP) and Omada setup.
Site 2 connects to site 1 over a VPN to reach the PBX and the File Server. 

I have vlans for voip, file, wifi, pc's

I have a wireless bridge (not in use) between both sites.  In the old setup, I only had one ISP and used the bridge to access the internet. 
Everything works fine, however, I would like to accomplish 2 things

- have the vpn running over the wireless connection because the bandwidh is much higer.  

- have a failover through the bridge in case a ISP goes offline (happens often).  If ISP 1 goes down, both sides need to access the internet through ISP 2 and vice versa.
  

I have only basic knowledge of networking and can't figure it out.  

Any help is greatly appreciated.