so I bought an audi a6, but it makes me feel weird into what my colleagues of other departments will think, like I'm earning way too much which I'm not, or have any kind of crazy ideas, besides I'm sort of young age. My dev department knows and I feel cool with that. The reason I want to know how I can handle it is because I think I need to use my office parking lots, and they will ofcourse notice.
This shouldn't be a problem and you shouldn't make it into one.
Carry on as normal. Drive to work, do your work, drive home from work. Say thank you to those that complement the car. If you're that worried about them judging you for having bought a more expensive vehicle, just add an 'I've been saving for a while and excited to finally get it!'. You don't need to justify what you've done to anyone at work.