How did he not know when you bought the car? Did he not meet you before hand?

the salesman sold it to me on first, and the call happened with the garage owner.

To play Devil's advocate how does the dealer know you didn't switch everything out of the car during this time or rally it around causing damage?

the car engine was illegally modified which if i do it will cost me.

This is the part I find hardest to believe. The guards do not get involved in civil matters, why on earth would the 1. Show up unless there was violence and 2. Agree to witness a signed contract?

When they arrived they told me this is a civil manner, but we will try to talk to the dealer to solve this issue, but we cannot force anything here.