Before the engine stops it probably has enough diesel (lubrication) and if the gasoline percentage gets to high the engine will stop, so the damage can be none/minimal.
Suck the fuel out and or take the feeder line of before the high pressure pump and let the electric feeder pump , pump the rest out.
Then fill up with 5 liter diesel connect the feeder pipe again and let the feeder pump circulate again then disconnect the feeder line again and push it out again with the feeder pump in a container...
Check if you can ignite a sample of the fuel with a lighter if it cant be ignited the diesel part will be high enough....
Fill it up completely with (bio)(lubricates better)diesel and circulate again with the feederpump ... the gasoline part will be so minimal that it will be no harm.... but a small portion ash free 2 stroke oil or high percentage biodiesel for lubrication.
Here is clip where they treat this problem in roughly the same manner.....car starts with no apperent damage
https://www.youtube.com/watch?v=eTbCZV0Uduc