Relearning Math (and eventually chemisty/physics) as an [older] adult

Does anyone have any recommendations for relearning (assume “from scratch”) math and later chemistry/physics?

I’m almost 50 and have a boy starting a kindergarten next school year.

He has a late bday so he will be almost 6 going in. We have done nothing to push him like some psycho parents do with young kids. But he shows an interest in numbers.

He got the multiplication principle literally the first time I tried poorly to explain it. He adds in his head. Nothing prodigy level but clearly has an interest in and ability to process basic arithmetic.

Assuming he gets in (lol, sounds absurd), he’s going to be doing 2-day classic school with one-day homeschool, next school year. I’m frankly a little daunted by the prospect of co-teaching this kid math in a few years and want to brush up.

I always got the concepts and was good at applying math to chemistry (one would hope, given my dad has a PhD in polymer chemistry) in college. But I remember nothing. And I wasn’t a good math student. One problem was my instructors at LSU didn’t speak much English, and I zoned out. As a lawyer, the most I do is calculate interest and maybe graph some stuff.

Anyway, I want to start as basic as possible. Like algebra and trig. And if I’m getting it just blaze through to calculus. We have a 3yo also, so I need this to stick for several years.

There’s so much junk out there, it’s hard to sort through. And I try to avoid Reddit holes.

TIA!