Will my hand become impure if I touch my bedsheets that have dried semen and precum on them after intercourse? Can I still pray on those bedsheets?
If your hand was dry and the Najis bed sheet was dry also, then your hand will not become Najis by such touching, Najasah (impurity) does not transfer between dry items. Najasah (impurity) transfers through transferring wetness only.الرطوبة المسرية.
Praying on such bed sheet is permissible when it is dry and your clothes and body touching it are dry as well, and you do not do Sajdah (Sojood) on the Najis part of the bed sheet.
Wassalam.