Is the continuous discharge of semen and other fluids considered سلس ( سلس is a type of ritual impurity in Islamic law, often translated as "incontinence" or "constant discharge" )? And how can one perform prayer in this state?

Ghusl is only obligatory upon verifying the emission of semen (mani) which necessitates it. If there is doubt, ghusl is not required. Semen discharged due to an illness does not necessitate ghusl according to the majority of scholars. A person afflicted with urinary incontinence (sils al-mani) should perform ablution for each prayer. One must turn away from obsessive thoughts (waswas) and not pay attention to them.