Dungeons and Dragons

So I have two groups

• Group 1 (ranger, druid, sorcerer, and barbarian)
• Group 2 (bard, wizard, barbarian)

We started the first session as one big group instead of two and it was chaotic. Everyone was talking over eachother and wasn't listening in general so I approached group one and asked if they wanted to split from group 2. They said yes. So in the world they kidnapped an npc from group 2 to try and sale and ditches group 2. 2 was surprised at first but was happy in the end. Group 1 ended up going north ditching group 2 thinking they were going to be tracked. 2 ended up making an alliance with the king (everyone's level 1 so I'm also having pacing problems) and went on their way to hunt down 1. 1 ended up killing the npc apon nearly getting killed to a necromancer (I've improvised everything thus far) and ran. In the next session I made a dungeon for both 1 and 2 but 2 haven't got to do it yet because of scheduling issues. (Last session was 3 months ago) and 1 is getting impatient but don't want 2 rob 2 of an epic fight once they meet instead of making a new world. I ended up doing another session and a town got burnt down and a water supply poisoned. They ended up stopping the poison by freezing the river and escorting all of the poisoned ice out. In my sessions things go really fast. Any help or ideas?