@Tij @kaia @meso
When (Adverb, indicating time) the (article, like 'a') cute (A word often used to describe the aesthetic of things like babies or puppies, often things that trigger a maternal or paternal instinct. when used on adults its often a measure of attractiveness, e.g 'he's cute' = 'he's attractive') tomboy (Woman who acts and dress like a man, usually shorter hair and preferring trousers or shorts to skirts. often enjoys sports and sometimes video games) waitress (Female version of waiter, serves food or drink in dining establishments.) is putting (applying, this case in a social context, e.g 'putting the pressure on') the rizz (shortening of 'charisma', if someone is charismatic they have 'rizz', if someone is socially inept they may have 'ohio rizz') on me (in this case 'the putting' is being shown to be on the writer/author of the post) while (whilst, indicating action, combined with the time aspect this gives a clear indication of the situation.) eating out (dining outside of the house where food is normally eaten, usually at a restaurant or bar.) with (indication in this case is with someone or something.) my (belonging to) BF (contraction of BoyFriend,)

To phrase another way:
Whilst dining out with my boyfriend, a cute tomboy waitress began flirting with me.