The first episode of a series is often confusing, as you try to work out who people are and what they're doing. This is particularly true of crime series. I've watched some that seem to be telling several different stories at the beginning and don't make much sense until eventually they join up. You have to give it time to get going.
The jargon is a bit confusing but I don't think it matters if you don't know what most of it means. If it's important for us to what "A1 on the Matrix" means, for example, presumably they will tell us. As for the unfortunately-named CHIS, I shall say no more.
I like Kelly Macdonald and think that she will be a good lead character. Everyone seems to remember her from Trainspotting, but to me she is the sweet police officer in Giri/Haji. (An excellent series, by the way, and well worth watching.)
I also like Steve with a beard, though I may be in a minority. He is rather cute - I like a man in a waistcoat. He does look even more irritated than usual. Possibly constipated as a result of all that codeine.