When I want to find out whether a teacher is any good, I look at the number of lessons their students have taken with them. This method doesn't always work, but is in my opinion the most reliable one.
It's definitely tricky and I have limited experience as I've only taken lessons with one tutor. I tried to take lessons with other teachers, but it didn't work out. One teacher failed to respond to my initial messages (they were on vacation, but hadn't mentioned that on their page. They responded a month or so later). Another one had limited time slots and had to reschedule the first lesson (sickness, understandable. By that time I had already found a great tutor).
I think one metric that is somewhat reliable is the number of students who take more than one lesson. If many students are willing to keep paying and come back for more, the person must be 'good' for some people. It doesn't guarantee they will be 'good' for you though. I suggest sending a text message to the teacher first to see if they might be a good fit. i.e. tell them what you hope to achieve and see how they respond.
There is a saying in English: "Money talks". In this context, if people are willing to keep spending, there must be something of value to be had or they would simply go somewhere else.
