Hey Oldman, nice video
The first thing I noticed was how high you were in your transitions- when you pass the guard, and early on you attempt mount a couple of times- you leave a lot of space and don't really have control of the other guy. You are hoping that the speed of the transition will make up for the lack of control. It will not work with a more experienced grappler who will use the space to escape.
On the same note, later on there are a few submissions attempted, but again there is often a lot of space left, and sometimes you are sacrificing your position for a submission- I think there your partner attempted a strangle from half guard, which is a) impossible to finish and b) allows his opponent to reverse him. Another example is when your opponent takes your back, he never properly secures his position, and so inevitably ends up in guard. Lastly, when you try an arm bar from mount, you are again too high in the transition and you leave masses of space- relying on speed rather than technique.
Both of you are very flat backed in guard. In order to pull of arm bars and the like you have to be very mobile on your back, which is very difficult when it is flat. What tends to happen is your arm bar attempt becomes a guard pass for the other guy.
But heck, we were all like that when we started(and I'm still often guilty of it). I have two pieces of advice for you in how to specifically improve your weak points:
1) Practice lots and lots of shrimping drills. These may seem a bit silly, but they are excellent at teaching mobility off your back and creating space in inferior positions. I have a judo instructor who always makes us practice lots of shrimping at the beginning of class, and it very quickly improves your bottom game. It helps in all of your sweeps and submissions, because they all require mobility and control.
2) Try rolling while just focusing on position, rather than submissions. Rather than trying to get a submission from the top, try and pass the guard, then go right around your opponent's body maintaining top control- it will really help you learn to transition tightly, without leaving any space. We often do an "around the world" drill, with one guy going from scarf hold, to various side controls, to north south position, and round the other side into mount, finishing where you started. Try it at first with no resistance, then with 50%, then all out. It shows you pretty quickly where you are leaving space. The aim is to go nice and slowly, maintaining control the whole way round while advancing position.
Lastly, that was a loooong roll! I would be just as dead as you were at the end of that.