i think peeing after ejaculating, cleans.out the urethra, preventing any cum drying and causing irritation
This is true.
It’s normal to have to go soon after ejaculating. It’s also normal to not be able to go so soon after ejaculating (it can simply be difficult to pee too soon afterward) so you may have to wait a little while before doing so.
My friend (my age) genuinely didn’t know this and thought something was wrong with him. It doesn’t sound like much but this kinda stuff should be taught.