The interests of people who are lesbian, gay, bisexual, transsexual or intersexual are represented by organisations, for example the Organisation for Lesbian and Gay people https://www.lsvd.de/
Please visit https://www.thueringen.de/mam/th10/ab/gender_und_orientierung.pdf
for additional information.
If Your child is treated badly because of his or her sexual orientation, You can find support at http://www.vlsp.de/