Ask HN: What math should I know well to be able to learn ML

I want to learn ML and deep learning and since it involves a lot of math, could anybody pinpoint exactly what domains should I renew for this task, hopefully with references to some good books or educational material. I studied math and computer science 20++ years ago on university of mathematics where I had 20 different math subjects but in my last 15 years of work I forgot most of it since I don't use any more advanced math on my current job as software architect where I deal with automation, development, system design, operating systems, integrations etc. I am very experienced in many different IT domains but I would like to attack this problem in more deep way then just starting immediately with online courses or tutorials (but not so deep that it consumes all my free time, nor would I want it, I have many different hobbies and interest). My end goal is to know to apply ML methods and understand enough of it to improve/troubleshot anything that doesn't fit immediatel