The part is designed in such a way that it does not yet fit the Opel perfectly.
You have to heat the part with a hairdryer (or preferably a hot air dryer) and press it onto the Opel so that it fits perfectly.
hen it's best to stick it on with plastic glue and wait.
I also put a green foil underneath so that in extreme cases it doesn't damage the Opel when it is removed.