>but my friend who lived in Tajikistan until he was a teenager said that Tajik is closer to Uzbek than Farsi
Doesn't sound feasible, as a native Turkic speaker, Uzbek is a language I can somewhat understand unlike anything Indo-European. A dialect of it seems influenced at most
https://en.wikipedia.org/wiki/Tajik_language?useskin=vector
>The standard language is based on the northwestern dialects of Tajik (region of the old major city of Samarqand), which have been somewhat influenced by the neighbouring Uzbek language as a result of geographical proximity
>This Tajik–Uzbek bilingualism has had a strong influence on the phonology, morphology, and syntax of Bukharan Tajik
In any case, if u want to learn Tajik, you should learn it instead of another language close to it