Hi there,
Your freind's liability car insurance should cover damages inflicted by their car on third parties. However, Swiss car insurance providers do not generally deliver worldwide or even Europe-wide coverage. Ask your friend to confirm whether their insurance covers the country you are visiting with their insurer (by requesting a green card, for example).
Compulsory liability car insurance does not cover damages to your friends car. If you have an accident and your friend claims on their liability car insurance, their premiums may go up (loss of claims-free discounts) and they will have to pay a deductible.
You can protect both yours and your friend's finances by adding the "Third-party car" rider to your personal liability insurance policy. This rider covers the costs of damages to the borrowed car and the deductible and premium difference.
Best regards from Moneyguru
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