Help fault after fault here!!

[TheNightFurries]

My partners beeing having issues with the car for the last couple of weeks going into limp mode

Turn the engine off then on and it's fine but has been doing it intermittently for weeks

Also had fuel rail pressure error so have changed this sensor and the filter (which CLEARLY hadn't been done on the service).

Now it's come up DPF full, one mechanic just tried to do a force regeneration on it but it failed due to going into limp mode (may have been because of the fuel issue) but also the cooling fans started instantly kicking in so the temp wouldn't get up to temp so also changed the cooling temp sender as this can be caused as a back up if the sensor fails 

After taking it for a spin to try to see if the issue was fixed it still went into limp mode and cutting out as if someone's just ripped the battery out then draining the battery and even a jump start wouldn't start it so we charged the battery 

Now it's thrown up oil pressure low stop engine light to see that it's oil level is now stupidly high so after and oil change and filter (possibly 7/8L came out) 

It's now not starting or even cranking as if the battery's just completely dead that there's nothing in it to even crank it over although battery's fully charged and says heath it good 

And now I'm at a brick wall I really don't know what else to try