Springer Nature interview questions

I applied online, after around 2 weeks I received a request for a fist interview. This interview was very easy and basic, just to get to know each other. Before and during the interview I had to lower, two times, my salary expectations. At the end the salary was 50k, no negotiation. I decided to go further, just to give it a try. Before the end of the interview I got noticed about that the following step would be an assessment, very general. After a week or so I received a positive feedback and we scheduled the assessment. They gave me 5 days for the assessment. Before receiving the work I thought "It is a loose deadline, so I would be able to do it during my normal activities". I received the assessment and realized that It was not so loose. They give you 4 manuscripts, you have to review three of them in 5 days. Sounds like working for days for free. If you are familiar with the topics, you can review them in 4-5 hours, if not one full day of working of even more. The topics were very far from my background, looks like they were looking for someone to review everything about engineering. I withdraw my application.