邦夫は自分の下品なテーブルマナーをあらためようとしなかったので、我々はがまんしなければならなかった。

、。

Kunio wouldn't try to improve his vulgar table manners, so we had to put up with them.

Literal

Kunio [topic-は] self [possessive-の] vulgar table-manners [object-を] try-to-fix-[negative-past-しなかった] [because-ので], we [topic-は] endure-[had-to-なければならなかった]

The volitional-negative pattern ~ようとしなかった ('didn't try to X') comes from ~ようとする ('to try to X') in the negative past. Stacked with ので (because) to form the causal clause. 下品 (げひん) = vulgar, low-class, distinct from its antonym 上品 (refined, elegant). A nice worked example of multi-clause structure.