Newbie looking for some help please

Hi everyone hope your well I’m a newbie to fords and purchased a 2008 Fiesta 1.4 TDCI MK6 back in April 2021 and unfortunately I’m still having a few issues with the car 

Im hoping someone might be able to help me out with the issues and point me in the right direction 

The first issue is since purchasing the vehicle it stutters under heavy loads like going up hills etc but never any fault codes or lights. I changed the fuel filter to no avail and then a month later a light popped up. Fault code P0100 MASS AIR FLOW SENSOR I replaced the sensor with a brand new Bosch unit and the light came back on after a little drive so again assumed it wasn’t that after all. I took the light off again and since then it’s been running perfectly with no stuttering since May until today when it started to stutter again and the light popped back on. 
 

This time though 2 x codes were showing 

P0100

P0100 P

Would anyone have any ideas what the fault could now be ? Could it be the EGR valve causing the issues with the mass sensor ? Or would that have its own code ? 

My 2nd issue which again has been there since purchasing in April is the DOOR OPEN WARNING light on the dash it’s intermittent with the passenger front and driver side rear doors only. But happens daily at different times 

They are fully closed but due to them showing open at the time we can’t lock the car as it instantly opens back up having to take everything out of the car 

I have tried to remove the fuse to lock the car manually but that won’t work so I desperately need some help to point out what I can do to resolve these 2 x door issues 

One minute they are fine then suddenly it will pop up, I’ve tried the WD40 in the latches etc but to no avail so any help would be gratefully received on both issues 

sorry for the long post I’ve tried to do things my self but I now need help and advice 😩

Thank you