in a world of your own
US /ɪn ə wɜrld əv jʊər oʊn/
UK /ɪn ə wɜrld əv jʊər oʊn/

1.
in seiner/ihrer eigenen Welt, in Gedanken versunken
living in your own thoughts and imagination, often unaware of what is happening around you
:
•
She's often in a world of her own, dreaming about her next novel.
Sie ist oft in ihrer eigenen Welt, träumt von ihrem nächsten Roman.
•
He was so deep in a world of his own that he didn't hear me call his name.
Er war so tief in seiner eigenen Welt, dass er mich nicht rufen hörte.