That is hearsay. You can object if the witness states something she only heard from someone else. A witness can testify only to what he or she actually saw. You should practice saying your side of the case. Make a written outline or checklist to use at the hearing.
Photos speak a thousand words.
If you have a complaint about the condition of your apartment, take photos if you can. Be prepared to say when the photos were taken and by whom. The District Justice may decide the case right in the courtroom after he has heard all the evidence. You have a right to appeal. Appeals are filed at the local County Courthouse.