does anyone have any good explanations as to why we can't have sex before marriage or have bf/gf just by using our common sence? like how would someone that believes in god and the last day know that sex before marriage is not allowed if he can't read the quran?

anyone know what the exact definition of adultery and fornication according to the quran alone? i believe in 1 god and the last day and want to follow god's laws but my problem is can't really read arabic and i refuse to believe a translator if i can't verify what i read so i don't follow everything i read in a translation if i can't verfy it by god's words or if it's not common sence so i think my only opition is to learn god's words to be able to know.