Should one believe dreams that indicate a suitor is deceitful and a liar, or ignore them and rely on apparent reality?

As long as you are content with your fiancé and nothing has appeared from him that blemishes his religion or character, then you should not leave him because of dreams. A dream could be from one's own thoughts or from Satan, and not every dream is truthful. It is not permissible to annul an engagement based solely on a dream whose truthfulness or correct interpretation cannot be ascertained. The correct approach is to disregard dreams and rely on reality, to proceed with the engagement, and to perform Istikhara (prayer for guidance). The one who performs Istikhara proceeds with the matter after Istikhara unless Allah diverts him from it.