mam na telefone chlapa a zle sa mi pise po slovensky a hovori po anglicky. My translation makes little sense. "I am on the phone with my boyfriend making mistakes writing in slovak and thinking in english" I have no translation for "mam"
I'm on the phone with (some) guy (boyfriend is possible, but IMHO improbable) and it's difficult for me write in Slovak and talk in English at a time.
You're not too far, I'd however translate it like: "I'm on the phone with a man and it is causing me problems to type in Slovak and speak in English." "zle sa mi píše po slovensky" = could be better "I don't feel very comfortable writing in Slovak"... or "I cannot type in Slovak properly" mam = mám = I have Mám na telefóne niekoho = I am on the phone with somebody chlap - could be also a boyfriend, but it's not very nice name to a bf, therefore I'd rather say it's generally a man/boy...