boys can be so weird, what do I do?

lowk in shock still even tho its been 5 hours

 im transferring schools soon so i had to go to the library to return my school computer and ran into my good friend jose, jose doesnt speak english so i offered help to translate what was wrong with his computer. note: Jose is dating my best friend Kiri. afterward, i walked him to class, as i was walking with him he began to suggest a threesum with me, kiri, and him. which i found funny at the time, but then it got worse. he started saying i was a sexual freak and he knew i was probably good in bed etc. i continued to shrug it off but i began to raise an eyebrow. we got to his class and before he knocked on the door, he dabbed me up and pinned me to the wall and looked me in the eye, i awkwardly rushed away and he told me to come back and said "cmon, just give me a kiss" nd tried to pull me in..... i said "no?! youre with kiri! im telling her" and i rushed away to leave the hallway and he shouted for me to come back and it was "just a joke" i went back to class and told her other bestfriend and she didnt believe me. ok so? its not ab her idgaf. for some reason, her other bestfriend told her rather than me. i met up with kiri after school and tried telling her the truth and she flat out said "I dont believe you." and said it was my fault because i always brought up the topic of threesums, when i legit havent? her friends began lying to her and saying that they went to the library with him even tho he was alone. what should i do? how do i make her believe me?