Use a better VPN that gives at least as much BW than your ISP.

Of course it will slow it down a bit, since the net is routed through a tunnel which means a lot of servers have to communicate with eachother.

But if the VPN BW is greater or at least as much as your ISP's then it should be no problem.

For example if you have a 1MB/S internet, then you'd look for a VPN that gives at least that much, and then who knows as a net result you will get 0.9 MB/S after the routing and all of that.