Use the classified ad platform's rating system. Check the reviews from sellers. But bear in mind that reviews can also be bogus, especially if there are some very good and some very bad reviews.
Be suspicious if an offer is obviously too cheap.
For purchases involving large amounts of money, the transaction should be carried out via a trust company that you have chosen yourself.
Be sceptical if the merchant claims to be located in Switzerland but wants the payment to be sent abroad.
When transferring money, make sure that the seller and the account holder are identical.
Choose the most secure payment/delivery options (e.g. cash on delivery).
Money transfer services are often misused by fraudsters as these payments cannot be tracked.
Ideally, you should collect the goods in person and pay for them then.
Ignore any requests to provide a copy of your passport or ID card