[4] The usage of such Sino-Japanese words also increase in formal or literary contexts, and in expressions of abstract or complex ideas.
Japanese and Korean aren't tonal languages, but Chinese languages are tonal, which means that the proper pronunciation of a syllable for a word is important for communication, as well as the proper tone when pronouncing a word.
When Chinese symbols (Hanzi) are used for writing in Korean (which are called "Hanja") and in Japanese (which are called "Kanji"), sometimes a few words can be understood in a sentence, but an entire sentence is highly unlikely to be understood even in writing.
Japanese and Korean have their own writing systems which are different from Hanzi, so entirely sentences aren't likely to be fully written in borrowed Chinese symbols.
The table below shows some lexical similarity values for pairs of selected Romance, Germanic, and Slavic languages, as collected and published by Ethnologue.