The word for but in Lithuanian is very similar: bet.

There is another word that you need to know that is similar to but, but also means and. It is pretty simple: o.

Think of it as however, because o introduces a different or opposite idea:

Mano vardas yra Laimis, o tavo? My name is Laimis, and yours?
Jis vardu Vytautas, o ji? Hi is called Vytautas, but her?
Labas! Yra tėvas? O mama? O brolis? Hi! Is father there? And mother? And brother?
Mano tėvo vardas Kazys, o ne Darius. My father's name is Kazys, not Darius.