"He often buys milk here."
Translation:Často tady kupuje mléko.
I am not very happy with the order you managed to pass with. It is super marginal. As if TADY was an afterthough. Or you are trying to point out that it is TADY. The word order is brutal in Czech. You would say "On tady casto kupuje mleko" but when you skip ON, one would swap TADY and CASTO and say "Casto tady kupuje mleko" as if TADY insisted to be the second word of a sentence no matter what. My tip? Czech girlfriend
It may seem so, there is a lot of freedom here:
Často tady kupuje mléko.
Kupuje tady často mléko.
Tady často kupuje mléko.
Tady kupuje často mléko.
Are all almost the same. And more combinations are certainly possible if you want to emphasize some of the words.
Mléko tady často kupuje.
Mléko tady kupuje často.
Mléko kupuje často tady.