Even Latvians and Lithuanians cannot understand each other. They won’t have a meaningful conversation. Older generation Lithuanians and Latvians uses Russian, while younger generation uses English for communication.
Belarusian has more Baltic loan-words than other Slavic languages. Especially the north-western dialect of Belarusian. As well as some grammatical features entered Belarusian from Lithuanian. Other than that any Slavic language is a lot more closer to Belarusian than Lithuanian or Latvian.
Slavic loan-words were removed from literary Lithuanian during codification of standard Lithuanians. Latvians removed Germanic loan-words from standard Latvian. Both replaced Slavic and Germanic loan-words with Baltic word borrowing them from each other. Or replaced with neologisms.
Colloquial Lithuanian , especial south-eastern dialect and colloquial Latvian have Slavic loan-words.