All races of people have sex for pleasure and reproduction.
Advanced races of people do not have the amount of illnesses we have because they have overcome them and do not continue to promote them.
I do not know if the visiting race of humans in particular has any homosexuality. I only know from alien life that homosexuality is not common to all races, and not unheard of in some. I asked for further specific information and my alien friends declined to answer, I believe to prevent any misunderstanding or misperception on my part or on other people's parts who I would repeat the information to.
The ALFs, two races who were each creating their own hybrid people with the use of some humans, were mixing our genetics via the hybrid people back into their own races over some number of generations. It was done by technology and medicine, but I do not have specific knowledge or understanding of the processes.