First ever homebrew!

Came out not bad. But the starting temperature was a little high and it has a slight tangy flavour.

I'm trying to find a way to better control the fermentation temperature on the cheap. Any tips appreciated!

One question I do have... After leaving in the bottles for a couple of weeks I've noticed a white residue is settling on the bottom of the bottle. Is this normal? (Pic of sediment in comments)