I have a lot to say here :)
The most painful thing for me was fighting for a salary raise. You have to ask really hard for even a small salary raise. Your manager will then tell you that they will discuss it with their management, and you have to wait for the answer for at least 3 months. I really had a case waiting for approval for a year. Another raise I got was just a counteroffer. So you can imagine that getting a regular salary raise is a struggle.
Salaries are well below market rate for the EU and Poland. So that's why a lot of people come and go fast. They need to get some money while looking for a better job.
The second point here is about how pointless management is in the company. There is a delivery manager position whose responsibility is having 1-1 meetings with you sometimes, having calls with clients, and deciding about your salary raises. They do not take any part in your actual work and project. They are just sitting there "doing" something.
I was working on a project that was following an outstaff model, where the company itself just gets money for your work and pays you a part of it.
I was ok with that until they started selling me to the client as a really senior engineer, while my paycheck didn't grow (got a small raise after 3 months of struggling, though). Meanwhile, the client's expectations were really high, the stress level was growing, and the project was just really bad. Also, the work schedule was bad, and the client wanted the team to work till 9 PM for free. So I had to start working really late, finishing the work late as well.
After complaining about all of that to the management with clear examples and arguments, they decided that my communication was unprofessional and I was unreliable, so they introduced a ridiculous personal improvement plan along with a notification that they would not help me with a relocation benefit until I completed the plan. The manager was supposed to track some metrics of me leading the team and doing a lot more. One of the points in the plan was to successfully release the project to production. Let me remind you that the manager doesn't really take part in your working processes. So my manager wanted to track progress on the project without even knowing the release date of the project.
That was the moment I realized the company is really bad and resigned.
All in all, this is a very random company with management just getting their salaries, pretending to do work, and telling you how you should communicate and do the job yourself.