- What filament should be used eg for prints that need to withstand a little more heat such as in the car?
Pet-g is probably the best basic filament for heat resistant prints.

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


- What equipment is needed in any case?
Thin metal scrapers, foam sanding blocks, micro files, acetone, print glue, a light penetrating lubricant.

- How much KG filament should I get to start with?
1 kg red pla, 1 kg red pet-g, 1kg red tpu. Red filament is the easisest to use.

- Is there anything I have to pay special attention to?
Everything !
:-)

And as for pruinters - anything BUT an ender 3.