Counteroffer and total chaos from HR: hear them out or leave clean?

Hi all, I've been at a large multinational for almost 3 years, on an apprenticeship contract (I'm in Germany), working in industrial automation software.

Over the past few months I reported my manager's inappropriate behavior to HR. It kept getting worse, to the point where I was being sent on business trips alone, even though my contract legally requires a tutor with the same job to accompany me. The environment got more and more toxic, so I started looking around. When I was almost sure I'd get an offer, I had a chat with HR, who told me my manager was going to be fired. Nothing, however, about my own situation. The following week I left alone on a trip for a very high-profile client, and shortly after I handed in my resignation.

That's when the chaos started: calls and messages from my department head, HR, another manager and a colleague, all saying the same thing: please stay, you're important, name your price and we'll give it to you. Even now, while I'm away on this trip, they keep asking to sit down and talk, saying my projects are critical and that my leaving would mean losing them.

The context makes me think twice, though. The company isn't doing well financially, and about 15 people from my department have left in recent months, with no counteroffers that I noticed for any of them. The new company is offering me +40% on my salary. Was I underpaid? Yes, and I know it.

On the other hand, my manager will be gone and replaced by a colleague I get along with really well. But this insistence worries me. It feels like they're desperate to keep me because of the workload coming in the next few months.

I want to leave on good terms and keep the door open, since the company has a strong presence in my area. Does it make sense to listen to the counteroffer, or am I just risking complicating things? Any advice is welcome, thanks.

Author: controlsys