I assume if you're based outside of EU you were paid as a contractor? In that case you can start a legal dunning process (gerichtliches Mahnverfahren), that's actually surprisingly easy to start, most municipalities provide it as an online service. The court will ask you to provide some proof of the unpaid services you provided and send a court order to the company, most companies crater after that and pay. Once you…
Yes, I was hired as a contractor. The company is based in Köhlstraße, do you know which municipality website I need to file the complaint from?
Cologne has only one district court (Amtsgericht), that's https://www.ag-koeln.nrw.de/
Of the various Zwangsvollstrecking I think the Forderungsvollstreckung (you want to force somebody to pay their bill) is the relevant one https://www.justiz.nrw/BS/lebenslagen/zivilrecht/Zwangsvolls...
I'm not familiar in this legal area. You'll need at least somebody to translate the documents. I know one (well, a German resident) can do everything themselves for very low cost, I think 30 Euro. That's what contractors in Germany do when their bills are not paid.
Basically you tell the local court your demand, the court will notify the company and if they don't pay then the court will find ways to get the money. All the way to literally send somebody to their office and take their printer, office chair or company car and sell it. That part of justice is sweet (and funny) but usually it's letters send back and forth.