Recover House Deposit

I'm seeking legal assistance to recover my house deposit that my landlord refuses to return (frankfurt, last month of rent sept 2023). I've written to the landlord multiple times by emails, but they have never replied and not provided a specific reason for withholding the deposit. No damage at all was done and I have it confirmed by email by the house agency. The agency of course is not helpful in helping at all.

Requirements:
- Experience in tenant-landlord disputes
- Knowledge of local rental laws
- Strong negotiation skills
- Ability to draft legal letters or documents

Ideal Skills:
- Legal background or paralegal experience
- Previous success in recovering deposits
- Good communication skills

Please provide a strategy for resolution and any related experience.