My partner has Lumpy sperm and vitamin c and zink seem to help :)
I think liquification normally happens after about 30 minutes...but I'm not sure what "not completed" after two hours means. It could mean that is was not liquefied at all, or maybe it means it was partially liquefied after two hours. But if your doctor said it's nothing to worry about, it probably isn't.
As for supplements, I'm not sure what's suggested for liquification or volume specifically, but I know certain vitamins (like vitamin c and e) and amino acids like l-carnitine can help improve sperm count and function.
There are also vitamins formulations out there, specifically formulated to help men's fertility.
Best of luck to you!