Do you mean the long screw with the retaining Circlip (see : https://www.gunspares.co.uk/products...werkbau-Sport/) which needs removing before the screw can be unscrewed fully from the Trigger (with the Circlip in place it only unscrews two or three turns and then binds hard).
If it's something else, a piccy of the affected part would help in identifying the problem. Also, the above reference show a list of available parts for the FWB Sport your Trigger spring might be available from them (or if not, Knibbs Airgun Spares might be able to help)
HTH, Vic Thompson.