Law / How do I verify a Polish company's existence? [240]

Hi, I need your support.
I've a new supplier and I need to check if it's reliable or not, especially because they are asking for 100% pre-payment.

Company details are

ANWA Sp. Z o.o
02-384 Warszawa
ul. Wlodarzewska 59 A lok.8
NIP 526-27-35-219
Reg. 015574821

Thanks for your feedback