Right here we go , I bought a 2020 focus 1.5 ecoblue vingale end of October from a " reputable " dealership, after having it for 4 day the engine light came on ! I took it back and it needed a new dpf and sensor ,it took 2 weeks for them to do it as ford has a back log for parts having to come from Germany, anyway I got it back it back and 2 days later the light cam on again and it's back at the dealership this time it's the MAF sensor ! all the repairs are at their cost and they supply me with a car while mine is of the road . Now the question is have I bought a lemon? I really love the car It is everything I was looking for ,I could give it back but I'm don't have the use of any other cars so it would be difficult to get about, get to work and look for anything else ,I know the car was on the car front for a couple of months so probably not driven alot would this be a problem.  What do you all think 🤔 

I would expect some low battery faults if it'd been sat on the forecourt for a while.  But the DPF isn't filling up without the engine running, so needing a new one so soon after purchase is a bit of a concern.

Can't remember seeing one of these need a new MAF at 4 years old either.  Which could suggest that isn't actually the fault and the light will just reappear within a few days again.  Unfortunately Ford have to follow certain 'repair procedures' when it's a warranty repair, so they may choose to replace some parts as a cheaper option than spending a lot of labour time diagnosing a fault.

Difficult to say whether you've bought a lemon or whether it will be fine after these initial repairs are complete.  It's probably worth keeping it for now, though I might be tempted to keep an eye out for similar cars on the market in case you do need to make a quick change in the near future.

Thanks Tom 👍

I'd give it them back👍

What is the service history and mileage (although often a joke?)
See:
https://www.citizensadvice.org.uk/consumer/buying-or-repairing-a-car/problems-with-a-used-car/