one track mind

Translations
узкий кругозор
He has a one track mind when it comes to football and can't talk about anything else.
У него узкий кругозор, когда дело касается футбола, и он не может говорить ни о чем другом.
Definitions
A 'one track mind' refers to someone who is focused on only one thing or subject, often to the exclusion of everything else.
Words
mind

noun
ум
track

noun
трек
one

noun
единица