even if the promotion there is more difficult than in a medium-sized company.
Don’t be mistaken. Small companies and flat hierarchies mean that there are only a few positions for advancement within the company. Also, promotion usually means that you only delegate and supervise but rarely get to develop something yourself anymore. You have to want that, too.
I wouldn’t consider retirement provision as the decisive point in your stage of life. More important is first to use your human capital and find a job that pays you properly and opens up long-term opportunities. You will most likely change companies several times in your life anyway. By the way, I don’t buy the flat 20% more plus company car just by simply changing jobs. If it were that easy, you would have most likely changed long ago.
That doesn’t cost more than any A5 or the like.
ADAC says that over 5 years and 15,000km/year, that’s 68c/km. Since the OP has full equipment and drives less, certainly more. With about 10,000km per year, I also consider a company car nonsense, since it is underused. Rather a simple, sensible car. You can also have driving fun in the mountains with that. Driving straight on the highway is boring anyway until it becomes insanely dangerous...