They have two lines and big circles in front. Sometimes i not even hitting enemies that stand in front of me or enemies that are clearly in that big circle. It's multiple times over, so it can't be that i miss everything. Is it the same like in the first game?

It should be the same - you're definitely verifying that you're not just missing (via combat log)?

 

There is a very occasional issue with effects that travel like that, where the AoE that gets drawn when you're aiming doesn't precisely correspond to the reality of the level geography. The most common culprit are elevation changes - the drawn AoE definitely doesn't take into account inclines or elevation changes, but for many traveling effects a slight elevation bump will really change how it goes.

A related and less common, but still damning, issue is that obstacles that don't affect the drawn AoE may still affect the actual spell effect.

I haven't used twin stones nearly as much as other spells, so there may be bugs unique to it, but the few times I used it, it functioned like PoE1/

Yes, stairs etc. really mess up the aiming. It's because there aren't really stairs. It's just a lovely flat background that gives the illusion of elevation.