Zettle interview questions

I applied directly to their internal recruitment department with my CV and had an initial chat on the phone for some basic screening questions. I was then progressed to the next stage which was a take home technical test. It was a front end test to integrate with a third party API. The test is what you make of it. I spent a decent amount of time on it making sure it had CI and automated testing. They were impressed with my work and was then invited for a final face to face interview. They were again wanting to test my technical knowledge, but more focused on algorithms and data structures. This is a weak point of mine as I don't have any formal CS education. They weren't too bothered by this though. I was offered the position, but they lowballed the offer despite knowing what I was asking for. They weren't willing to pay any higher than £27k and at the time I was looking for £30k. I ended up going elsewhere to get considerably more than this. Salary negotiations soured my experience. I was also told they were looking to grow the team. It concerned me that the only engineers willing to accept those types of salaries are probably not going to be of the highest standard.