First there is a interview with HR, then there is a math test with about 8 questions where you have to explain the answers to an existing employee, then there is a teaching lesson, finally there is a interview with manager

This was the basic screening, but all they seemed to be interested in was how little money I was willing to work for, which was odd because the salary range was posted in the listing. The second red flag was that the 'tests' that they wanted to do as part of the process were only tangentially related to the job that they advertised for, while they couldn't answer anything about the nature of the actual work and didn't seem to be interested in things that were central to the type of work in the job listing. I couldn't tell whether the job posting was a bait-and-switch or whether they really didn't know what they were doing. The entire thing left a very bad taste in my mouth.