https://www.aids.gov/hiv-aids-basics...e-prophylaxis/
1) use condom.
2)bring her for STD/HIV test b4 have sex with her.
3)orally taken pill call Prep which stands for pre-exposure prophylaxis to prevent HIV. This pill must taken everyday & only for those who r currently HIV-negative. But u may find it troublesome have to take the pill everyday & definitely not cheap. For detail, pls refer to above website.
The more safest way is at home watch porn & pcc.
Anyway, bro, play safe, health come first