Testimony from witnesses is one way to present admissible evidence.
You cannot report the words of another person yourself. To be admissible as evidence, the words must be confirmed by the testimony of the person who spoke them.
You must provide the court clerk with a list of the names and addresses of the people you will call to testify.
Make sure you have the correct contact information for the witnesses you want the clerk to summon. You could be ordered to pay the costs for summoning witnesses the judge deems were summoned and made to appear for no reason.
The credibility and competency of an expert witness may be useful in supporting the arguments you present as part of your case.
For example, if your application concerns poorly executed work, it may be in your interest to call an expert witness such as a plumber or a building construction engineer.
Only an expert witness can attest to:
the poor quality of the work;
the cost of correcting the work;
the causal link between the work and the damages you have incurred.
You must generally pay for the services of an expert witness.
Witnesses are entitled to the reimbursement of their meal and travel costs. The amount of the reimbursement is established by regulation.
It is only at the end of the hearing that the judge identifies the witnesses to whom indemnities will be paid.