Does the vision of the Istikhara prayer change from one time to another, with different symbols between clear water and a burning fire, for the same subject of marriage?

Interpreting dreams is not within the purview of this website; one can consult specialists for that. A dream is not a reliable source for definitively determining progress or delay in a matter for which one has sought divine guidance (istikharah). The criterion, according to scholars, is the expansion of the chest (inner peace) and the facilitation of the matter.