I still think the movie is incredibly fun, don't get me wrong. It is also impossible to follow-up something as groundbreaking and legendary as Conan the Barbarian so let's cut them a break.

Basically Conan and his thief companion (which is played by a different actor because of health reasons) are wandering the countryside when approached by a royal family and offered riches for them to go on a quest escorting their daughter to some castle. They need to just make one stop along to way to gather some magic relic. Initially Conan declines the offer, but it is promised that if they complete the quest that Conan's woman interest, Valeria, from the first movie, can be brought back to life.
So off they go, gathering a a group of other individuals along the way, which include Zula (played by Grace Jones) a warrior who is the last of her tribe, and also Bombaata who is played by Wilt Chamberlain - who actually did a very good job considering this was his first acting role ever.

The movie is reasonably entertaining but is also a bit silly at times and this was intentional. It is also what I think is the biggest problem with this movie: It was decided that the movie could be more profitable if they toned down the sex and violence in order to achieve a PG rating. They had to cut a great deal of the content in order to achieve this. Basically, they wanted to market to kids. Unfortunately, for me and many other people, the ultra-violence of the first film is what made it so epic and without the violence parts of the film just seemed kind of dumb.
They also really went for it with special effects and well, it didn't really work out for them, and when you look at those scenes today they seem particularly silly whereas most of the puppets from Barbarian still hold up pretty reasonably well in modern times.
maybe if his mouth moved at all during the fight it would seem less dumb
Also, this was relatively early in Arnold's career and his English wasn't exactly up-to-scratch, so to speak. If you recall, he said very little in the first film and the narrator provided most of the necessary dialogue. In this movie, Arnold speaks quite a lot and I don't think that was a good idea.
I do want to share this picture because Andre the Giant is also in this film but is not credited because he was in a costume. However, we all probably think Arnold is massive but this pic kind of puts things in perspective.
This movie was nominated for 2 Razzies, which you may know is not a good thing. The poor box office results was a major catalyst in the shelfing of the 3rd movie in the trilogy, which was never released.