ヘタクソな人は英訳しないでください。英訳依頼者からのお願いです。

。。

People who are bad at this, please don't translate into English. This is a request from those of us asking for translations.

Literal

Unskilled [attr-な] person [topic-は] English-translate do-not-[please-でください]. English-translation-requester [from-から] [gen-の] request is.

ヘタクソ is a blunt intensification of 下手 — 'not just bad, really bad / hopeless' — with a slightly rude edge. The な is the copular attributive used with な-adjectives and nouns-turned-adjectives. 英訳依頼者からの is a nested particle phrase: からの turns the from-phrase into an attributive modifier on お願い, so the noun phrase reads 'a request (that comes) from translation requesters.' Stacking particles with の this way is a core Japanese strategy for building complex noun modifiers.