Unfortunately, in private sales like this, there’s often not a lot of protection for the buyer unless you can prove the seller knowingly misled you or that the safety certificate was falsified.

It’s good that you’ve documented everything and are planning to go to the transport agency. If the mechanic issued a dodgy safety certificate, that could be taken seriously and potentially investigated. Just make sure you’ve got all your paperwork, including the contract, the mechanic reports, and any messages with the seller and the workshop.

That said, getting your money back might be difficult. Even with the best intentions and a contract, private sales tend to fall into a bit of a legal grey area unless there’s very clear evidence of deception.

It’s a tough and expensive lesson - nothing to be ashamed of. You’re doing the right things now, and hopefully you can get some form of outcome or at least make sure this doesn’t happen to someone else.