HELP!!!! When i go to put the key into the fuel door and turn it the key only slightly turns and won’t unlock so i cannot put fuel in the car. Dunno what to do please help. 

Try some penetrating fluid in the lock, WD40 will do if that's all you've got.  If it frees up the lock, use some graphite lube afterwards to keep it moving.

Alternatively if you need a quick solution, break the flap open with a screwdriver and replace it in the future.

it might not be the case with you but just in case it helps others.  a couple of times in the past people have told me their key snapped off in the lock and they don't know what to do. I have then said I expect it has been stiff for a while. They say Yes, I say why didn't you oil it / fix it when you first noticed trouble. They then have this blank look on their face. Sorry if this was not you, but it is very often the case that people can save themselves grief by attending to problems early and not waiting until it's too late.  At least it's plastic (I think) so you can break it with damaging the actual car body. 

I have the exact same problem with my fiesta. Its so hard to open the filler flap. What I'd do is turn the key back and forth which hopefully then is able to turn the lock. My dad might take the lock off to have a look at it but try spraying WD40 to see if it helps.