It is almost impossible to fire long term employees in Germany. But getting proper employment is very difficult for this reason. Most people are on yearly contracts, part time jobs etc...
The share of part-time employment in Germany was 7.4% of all employment contracts in 2021. Nothing significant changed since then. https://www.destatis.de/DE/Themen/Arbeit/Arbeitsmarkt/Qualit...
https://doku.iab.de/arbeitsmarktdaten/Befristungen_bei_Neuei...
I already cited the share of term limited contracts above.
It’s not surprising that term limited contracts are a significant chunk of the Job offerings, even if they are a small share of the total contracts - a job posting that must be renewed annually will appear every year for the same position, while an unlimited contract only opens up when a replacement must be found or a new position is created. Another cause is that a lot of companies use a limited contract as a trial period and later convert to an unlimited contract at renewal time.
It is absolutely true that some sectors suffer from having a huge chunk of limited contracts (academia for example) and that there’s abuse (auxiliary teachers only being employed during the term and made redundant during vacations), but generalizing this to the entire German job market is neither warranted nor helpful.