We're flying SFO-FRA (UA), FRA-HAM (LH) on separate tickets. What happens with customs and immigration in FRA. I know we go through passport control--but does our luggage come out in FRA, get checked and then we place it back on a conveyor belt to get re-checked again (sort of like what happens in the US)? And then through additional screening?

And is 2hrs enough time? There is a FRA-HAM flight 2hrs after the UA flight and another at 3hrs.

Thanks