Sometimes you don't succeed no matter how hard you work at it. But I can tell you that anybody who made success in their life worked hard enough to deserve it.
Sometimes you don't succeed no matter how hard you work at it.
（いくら頑張っても成功しない時もある[＝成功するとは限らない]）
sometimes 〜 not = 〜とは限らない、〜でない時もある You don't always 〜でもOK
succeed = 成功する
no matter how ＋形容詞・副詞 = いくら〜でも
hard = 一生懸命
work at 〜 = 〜に取り組む、頑張る (ここでの it は一般的なものごとや、頑張っている対象を指します）
But I can tell you that anybody who made success in their life worked hard enough to deserve it.
I can tell you that = これだけは言える
anybody who made success = 成功した人は誰でも
in their life = その人の人生で 先行詞のanybodyは単数形なので、lifeの所有を表す代名詞はhis or her ですが、theirも同じようによく使われます。
worked hard enough = 十分に努力したのだ
to deserve it = （その成功を）得るに値するように
ちょっと長い文ですが、４段階に区切って文を作るとわかりやすいと思います。
①I can tell you that / ②anybody who made success in their life) / ③ worked hard enough / ④ to deserve it.
参考になれば嬉しいです！
Hard work do not always lead to success, but everyone who succeeded worked hard.
Hard work do not always lead to success, but everyone who succeeded worked hard.
Hard work・・努力
（努力はeffortでも良いと思います）
lead to success・・成功する、成功につながる
（成果があるという意味のpay offを使うこともできます）
日本 
