Bird,
Unfortunately, yours is a question for which there is no easy answer.
There are a variety of trigger designs on the market, and one of those may or may not be similar to the Beeman rifle you have.
Generally trigger adjustments are best left to a gunsmith because of the potential for a catastrophic accident.
Firearms manufacturers, gunsmiths, and even individuals have been sued by individuals injured in trigger-related accidents (or sued by the victim's survivors).
Most firearms magazines will no longer print information on how to lighten triggers.