I sold my Alfa some time ago, but going from memory:-
The screw behind the trigger is the overtravel.
The screw at 45deg downwards in front of the trigger guard sets trigger weight (but this interacts with the overtravel which also compresses a spring)
The main adjustment is the two small screws in front of the trigger.
Two stage.
With the gun unloaded but cocked, scew in the rear screw until gun fires, then back it off one turn.
Recock the gun and screw in the front screw until gun fires, then back off one and a half turns.
This is the basic two stage setting; you can play around from here, but only 1/8th turn at a time. Adjustment away from these settings is tricky as the adjustments interact.
It's all practically the same as the Tau7 here:-
http://www.pilkguns.com/tenp/sptau7.htm
At bottom of page there is a button for an exploded view. Although adjustments of Alfa and Tau are the same, the actual sear mechanisms are very different.
If you tap out the trigger pivot pin on the Alfa and remove the trigger, you will see how it oprates. Very simple and rustic. Make a sketch of the mechanism and that will help you to see what each adjustment does.
If you get lost, go back to factory setting and start again!!