As far as advanced trigger tweaking goes, it’s best left to the experts. However, a notable exception is the CZ 452 and 455 in either 22 or 17 HMR. Older models have notoriously stiff triggers. I shot an elderly 17HMR recently and it was more like pulling a tractor than a trigger!
Several friends have bought the superb Rimfire Magic CZ trigger kits. At just £13 it’s a no brainer and according to everyone I’ve spoken to they totally transform the rifle. Better still it’s an easy fit that doesn’t require a gunsmith, simply follow the instructions provided.