This seems like a tricky one.... HAPPEN doesn't really get used as a verb in English (I don't think??)....Maybe "Occur"? or "Do"
I happen ....(I happen to or I happen across (= I accidentally discover) You/They/We happen...never really gets used unless " happen to" and is usually used as a gentle disagreement:
John: "No one wants to watch this film, it's rubbish!" Jane: "Well, I happen to like it."
Does ACONTECER get used like this:
Eu aconteco jogo ukulele = "I happen to play ukulele" or "I do play ukulele"