Furthermore, I have the following questions:
- I use as OS only Linux (Ubuntu) and I think Cura and Blender as software should be suitable here? (I have experience in the design sector so I think the start here should be easier).
I'd recommend starting with PrusaSlicer over Cura. It also runs under Linux, but has a cleaner interface.

- What filament should be used eg for prints that need to withstand a little more heat such as in the car?
Up to ~70-80ºC, I'd recommend PETG
Up to ~90-100ºC, then ABS (But it's annoying to print)
Up to ~120ºC Nylon + Carbon Fibre (which can be quite easy to print, but will eat normal nozzles. Needs a hardened steel nozzle).

- Which filament should be used for all other prints?
PLA

- What equipment is needed in any case?
Get some decent allen keys and small pliers. I also like deburring tools (https://www.bunnings.com.au/irwin-po...-tool_p0097885). Some isopropyl alcohol (cleaning kind-99%, not hand washing kind). Some acetone. A spatula/scraper.

- How much KG filament should I get to start with?
1kg of each of your preferred materials would be a good starting point. I don't agree that it has to be red. Most colours print pretty similarly, The only colour I'd avoid at first is white (Most whites print fine, but some, such as eSuns ABS+, can be difficult).

Most filament suppliers offer free shipping if you buy over a certain amount. That may be an incentive to buy a certain number of spools to start. In my case I generally buy them in batches of 4 to 8 spools, depending on where the free shipping begins.

As for Ender 3 or Anycubic. Both are decent entry level printers. Of the two I'd probably choose the Anycubic (I prefer bearings over v-slot wheels, and the dual Z-axis is a better mechanical system), but be aware that there is a lot more community support for the Ender.