If the door has the correct panel gaps around then just move the strike plate slightly until it can open and close freely with the outer door handle raised
If its a case of pulling the handle upwards is not releasing the lock then you may need to adjust the lock or replace the bowden cable inside the door, which can stretch. Most find this and issue in summer not winter as heat makes it worse.
if it is indeed the Bowden cable, the part number is 51217038061 and they cost about £10.
They're a bit fiddly to fit, but if you plan a couple of hours to do it yourself, it's easily achievable
Try this..open the door and then close the latch with a screw driver and see if it opens easy or hard then ? that will tell you if it's in the door or it's the receptacle on the door frame which is maladjusted.