this stuff works like a charm
It's a multi-step process that can take awhile but you can win your fight against roaches.. because after awhile i managed to conquer the problem using these steps:
1) Plug up every hole and crack going into your apartment.. piping is very popular so use caulk or whatever to seal anything up coming into your apartment... the idea is for them to not come in from wherever they're hanging/breeding outside from... if you don't do this they will always find a way in... This is the hardest part but it is possible to find all the pathways into your apartment and plug them up...
2) Get yourself some Insect Growth Regulator.. this makes sure whatever is inside your apartment doesn't keep laying eggs and replicating... spray this all along your baseboards and any difficult to reach cracks behind/beside/on top of cabinets...
3) Get boric acid.. this stuff is the best since it doesn't go bad or dry up and will work forever the moment you lay it out... as long as you apply it lightly it will work the best...roaches like pushing their bodies against something so put this stuff in all the corners... underneath stoves/fridges... along corners of your wall...
4) If you must get poison or something get Advion Roach Gel... it doesn't work as well as boric acid since they learn to avoid it through smell and it dries up relatively quickly but it will do well the first time you throw it down....
5) Get glue traps... these are probably the most important since this will tell you lots of things... it will tell you how big of a problem you have... whether what you're doing is working... most importantly it will tell you WHERE they are coming from so pay a lot of attention to how they get trapped and it will most likely point you to a spot you missed from steps 1-4...
Other than that... keep things dry... roaches get thirsty more than hungry so keep the sink and everything dry.. if you have a leak you gotta fix it since that's prime breeding grounds for them... in fact if you have a roach problem it's likely you have a leak somewhere in the building... of course keep food and garbage tight and out of reach since they do get attracted to the smell but they can eat anything so it's not the most important thing to do...
Anyway good luck and feel free to ask questions since i know this can be a crazy problem to solve...
Not an expert nor pest control operator, but I am both fascinated by bugs (so I research them a lot) and also live in NYC, which means I have had to deal with German roaches my entire life.
It's not uncommon to find a dead adult every once in a while, my home has been kept clean and free of food or clutter even since I moved in, I still see an occasional dead or very weak adult (which in my case is because I administered a gel bait after deep cleaning the apartment right before moving in), sometimes they're dead because they dehydrated or because they simply reached their end of life (they can typically live for 3 - 6 months).
I would deep clean and remove any clutter from your home before you seek professional help (pest control had been a marked up business in my experience), and if you're still feeling paranoid you can use this gel; it's what I used to dispose of the infestation in my previous home and prevent one in my new home.
Before hiring an exterminator, try Advion Gel. Unfortunately it's not carried in stores so you will need to order it from Amazon.
Use this it works great!
https://www.amazon.com/dp/B0148W0WOE?ref=ppx_pop_mob_ap_share
I've used this stuff before:
https://www.amazon.com/advion-Plungers-Cockroach-Insecticide-Australian/dp/B00730QW70/
https://www.amazon.com/Advion-Cockroach-Tubes-Control-Syngenta/dp/B0148W0WOE/
Its probably the only thing I've ever used that decimated roaches and I would say I had a similar infestation level as you did. It was also apartment style but managed to do the job regardless of neighbor cleanliness.
They seem to be worse right now. This spray is pet-friendly (I'd take them away for a couple hours after you use it, though, just to be extra safe).
Spray around all base boards and entry ways to the house. I spray this stuff once every 6 months. The bait will take care of the current ones.
Here: https://www.amazon.com/gp/product/B000E28UQU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1