No compression car randomly starts. mechanic said it has no compression

code p 0300 refers to random/multiple cylinder misfires detected ===causes spark plugs ---HT leads ---injector/s--ignition coil/s---low compression---wiring
code p 0522 refers to engine oil pressure sensor/switch--low voltage ===causes wiring short to ground ---engine oil pressure sensor /switch---ECM
for the first code having to alter the accelerator position ( which tells the ECM to let in more fuel indicates either a low pressure in the fuel manifold or that the injectors need cleaning
At high way speeds when the engine appears to be running good , it is still possible to have random misfires caused by low fuel pressures and /or dirty injector tips
It would be a good idea to check the oil pressure with a mechanical gauge ,then replace the oil pressure sensor/switch

Bad Valves

What sort of mechanic is that,that can't diagnose your motor
or the misfire

If they did a cylinder leak down test, you wouldn't be here,you would
know the valves are bad & the head would be off & out for repair

The old give me money for nothing statement from a mechanic instead of knowing how to fix it.
code p0300 refers to random/ multiple cylinder/s misfire detected===causes--spark plug/s---HT lead/s---injector/s---ignition coil/s--low compression--wiring
code po303 refers to cylinder 3 misfire detected--- engine mechanical fault---wiring---ignition/ fuel system---injector --ECT/MAF sensor --- ECM
code p0306 refers to cylinder 6 misfire detected===causes --engine mechanical fault---wiring---ignition / fuel system---injector ---ECT/MAF sensor---ECM
code po316 refers to misfire detected during start up--first 1000 revs==causes--engine mechanical fault---wiring---ignition /fuel system---injector
code po2195 refers to heated oxygen sensor (HO2S) 1 bank 1 signal stuck lean===cayses ---HO2S---fuel pressure---injectors---intake leak
it also refers to O2S sensor 1 bank 1 same causes and also refers to HO2S 1 bank 1 implausible signal===causes --- short to positive---short to ground---Ho2S ---ECM
code po2196 refers to the same items as 2195 . some causes are also air intake restricted
Have a compression test done some where else and it will indicate the condition of the motor. The rest is sensors and wiring problems.

Well, I would probably get a second opinion next.
A random miss code is just that, the computer is seeing a loss of power on different cylinders at random times. If cylinder number one had a dead miss you should get a code 301.
It could be something mechanical such as a burnt valve or bad rings, but that is usually on one cylinder.
At least take it somewhere else and have a compression test done.

Run a compression check to ensure it is not mechanical, i.e. ring crack etc. Hook up to a scan tool and explore missfire monitoring via live data. Answer should lie within one of the afore mentioned.

I take it that the diesel filter has been changed and the air filter.

The cheapest solution would be to check the priming pump on the hand primer near the diesel pump. Prime the pump and then try to start it - does this work? These things sometimes leak air.

Another would be to get your compression tested (although that should already have been done.)

check fuel pump in tank could be overheating and going bad they have a thremal sensor that shuts the pump off to prevent a fire

Have back preasure to cat converter checked,this can also cause random missfire.Also check viscosity of oil.

check and clean battery treminals.Also do the same to starter wires