Is it normal not to know how to have sex at 27 ?

you get him aroused with foreplay this could involve dress up, perv talk, lapdancing, or even better spanking. then you start stripping. if hes a real man he should pull your skirt and panties down himself... if he dosent then do it yourself ;-) then it depends what type of sex:

vaginal
foreplay, strip, go!
he will stick his dick in your vagina and go back and forwards. you should have multiple orgasms and he will have one, wich afterwards he will stop.

oral.

if hes giving it to you, like before, foreplay, strip, go!
now, he will start licking your vagina. you should have some great orgasms!

if your giving it to him
foreplay, strip, go!
now you simply suck his dick. go up and down and he should eventually cum. if he cums in your mouth, either spit it out, or swallow it.

anal
foreplay ,strip, go!
now he should flip you over (or youll have to D.I.Y) now he could do it in many ways but either way he will have your ass hole on show. now he will put his dick in your ass and go in and out and in and ORGASM!

always wear a condom and take the birth control!