They said the only way to get rid of the pets is if the building management or landlord takes legal action against the couple. Supposedly this is underway (since Jan) but i have my doubts as the neighbours had shown no signs of change...
Seriously, money talks. Stop paying the rent now. If you want to be nice move out in a month and forfeit a month of your deposit. LL will not sue you, if they do you stay 2 months instead or even longer without paying them anything and they know is not worth the hassle.
One way to get the agent to help you is to force their agency. Go to the real estate agents office EVERY day; and complain tothat branch manager... tell them to find you a replacement flat, at their cost.
Do a search of that agency office (and the agent) and lodge your complaint there. You have nothing to loose. The agency OFFICE however... would now have skin in the game. They KNEW this was a problem flat, and they pretend ignorance. At the very least, you have lodged a complaint. True.... nothing may come out of it.
But then, these agents also accepted commission from the landlord !
If this is a co-broking lease, ie landlord used agent A and tenant used agent B, then you can find out who is agent A. Got both agents on the hook and let the agents pressure the landlord to let you out of the lease.
Ask your real-estate agent friends on how to lodge complaint with the EAA
Seriously put pressure on the agent; these real estate agents are resourceful... they will find a way to "help" you when it is their own skin on the line. So; put their skin in the game
The time it takes for your LL to sue you and even get you physically evicted is 3 months minimum. STOP paying the next two months rent, move out before the end of the month. Start moving shit as soon as you can after you find a new apartment. Take it as a learning lesson. Stay longer, look longer at any new places.