Is the fast valid if one masturbates again during a Ramadan day, and the semen is held back, then after urinating an unclear substance, whether it is semen or pre-seminal fluid, is discharged?

Masturbation is forbidden in Ramadan and outside of it. Its prohibition intensifies in Ramadan because it invalidates the fast and violates the sanctity of the obligatory worship. If semen is not discharged, the fast is not invalidated. However, if semen is discharged after it was held back, and you are certain it is semen, then ghusl (ritual bath) becomes obligatory, the fast is invalidated, and both making up the day and repentance become obligatory. If pre-seminal fluid (madhiy) is discharged, the fast is not invalidated.