For a property like your's, one of the international agencies would probably be best - Duna House, Otthon Centrum, A1 Ingatlan or maybe Central Home. They all have .hu website addresses. 120,000 euro would appear to be too high. This would put it in the luxury category and buyers of luxury properties in this part of outer District VII are few and far between.
Most of this post seems to be your own opinion and not really propped up by fact. The apartment you bought was in very much a secondary location, which is not popular with locals, at a price, which locals would not have paid then or now. Had you researched the market first, you would probably not have lost money. Decent properties are still selling well, prices are some of the lowest in Europe, when compared with real income and many people have made money here, even since 2003. The rental market for high quality properties is strong, as you seem to be witnessing too.
Bob, is it a new build or a classic apartment? Street or Courtyard facing? Which floor? Is there an elevator? What condition is the outside (in the case of a classic building)?
All these things greatly affect the price. The average on the link I posted above was €1k sq.m for Dis 7, but Classic buildings will be less.