Japanese people are not as kind as the foreign people think they are.
When they experience something unpleasant, they don't resist, but put up with it.
They may seem kind or generous, but they aren't really so.
ご質問ありがとうございます。
"Japanese people are not as kind as the foreign people think they are."＝「日本人は外国の人々が思うほど親切ではありません。」
"When they experience something unpleasant,"＝「何か嫌なことを経験すると、」
"they don't resist, but put up with it."＝「抵抗はせず、我慢するのです。」
"They may seem kind or generous, but they aren't really so."＝「親切や寛容に見えるかもしれないけど、実際はそうではありません。」
ご参考までに。
Japanese are not as nice as foreign people tend to believe, we just hold everything in.
この場合、次のような言い方ができますよ。
ーJapanese are not as nice as foreign people tend to believe, we just hold everything in.
「日本人は外国人が思っているほど親切ではない。私たちは我慢しているだけ」
ここの「我慢する」は to hold ... in は感情を抑制したり、怒っていても黙っているというニュアンスです。
ご参考まで！
アメリカ合衆国 
カナダ 
