Alleged disregard for the overtaking ban

Good evening! I am new to the forum and wanted to ask for advice in the following case. It is the case that I got a letter for the hearing because of a traffic violation and that is the disregard of the overtaking ban with a truck accused. As a witness is stated ****, POR VPI Bayreuth, although no one has stopped me nor do I remember having overtaken me without traffic. In the hearing not my license plate, but the trailer registration plate was indicated. phone request was only said that a witness saw this. Now I do not want to be wronged by someone and want proof that I really did. Was someone in a similar situation and could give me good advice? Thank you in advance and many greetings ***** the name of the official I removed -twindance/MT-moderation