Hi being a graphic designer i can tell you exactly what you need to do:
https://www.brandsoftheworld.com/logo/boxster
Go to this link and download this file onto a memory stick, basically its an Adobe Illustrator EPS files.
Don't worry that you will not be able to open the file, you would need Adobe Illustrator to be able to open the file.
Take the memory stick to a local sign company and ask them to cut it on vinyl to the size and colour you want. Dont get them to print the colour on the vinyl as it will fade eventually. Use actual coloured vinyl
Will cost about £10 max they may even apply them for you.
If not fit them yourself by wetting the door, apply on the graphic, slide it about till your happy with the position then gently squeeze out the water. if you get any small bubbles just pop them with a pin the push then water out. It will dry flat so don't sweat any small bubbles too much
or you can apply them dry but you get one chance to get it right.
Peter