what are the chances/percentage/probability to get infected?

Hello and welcome to e health forum.

The chances of HIV transmission vary with the mode of sexual intercourse. HIV is transmitted only by having multiple sexual encounters with a HIV positive person. The risk of HIV transmission ‎by a single sexual intercourse is about ‎‎0.08% (male to female), which is higher from that due to female to male ‎transmission (0.04%). ‎

Yes, contact with sexual fluids due to unprotected sex, does predispose you to risk of ‎HIV as well as other sexually transmitted infections like Herpes, Hepatitis B, Hepatitis C, gonorrhea, Chlamydia etc. ‎

Presence of other STDs, open sores, cuts, ulcers etc also increase the risk of infection via unprotected sexual intercourse.

The risk of transmission is increased by having a risky sexual behavior including:-

‎1. Having multiple sexual partners, ‎
‎2. Having intercourse without protection‎
‎3. Use of alcohol and Illegal drugs like methamphetamine, and other “party drug” use - can lead to risky sexual ‎behavior, due to reduced inhibition.‎
‎4. Low socio economic status, and psychiatric illnesses - can lead to higher rates of emotional distress, suicide ‎attempts, substance use, and risky sexual behavior. ‎

SAFE SEX - The ABC 's to prevent STDs include - ‎

A - Abstinence (not engaging in sex, or delaying first sex)‎
B - Being tested for HIV and Being faithful in marriage and monogamous relationships or reducing the number of ‎‎‎sexual partners
C - Use a Condom, correctly or consistently, if you are not faithful. ‎

Abstinence from vaginal, anal, and oral intercourse is the only 100% effective way to prevent HIV and other STDs. ‎‎‎The correct and consistent use of male latex condoms can reduce the risk of STD transmission, including HIV ‎‎‎infection. However, no protective method is 100% effective, and condom use cannot guarantee absolute ‎protection ‎‎against any STD. ‎

I hope this helps.