grammar

的確意見001+答案001都啱,唔係文法問題(reply us或reply us on the situation,preposition小事,唔影響意思,唔算咩grammar錯),而係內容問題,你得呢句,都唔知你前文有冇提過覆乜,你中文都冇提,英文夾硬+個the situation,下星期又變next Monday...多謝又講兩次...

Thank you for your information. They will reply us next week/Monday(睇返你真實意思), and we will inform you as soon as possible/asap(佢地覆我地,再通知你方結果/進度,先係完整意思卦?asap係官方接受嘅簡寫,但長寫都冇問題,重有禮貌d,其實禮貌又睇大家關係點,合作耐可以求其d,唔熟可以禮貌d,但唔代表要thank兩次)

giner2011 is correct!

(1) reply to somebody with something
(2) reply that

- The verb "reply" should not take an indirect object.
(correct use: reply to somebody with something)
- It is incorrect to put a preposition "on" in front of the adverbial "next Monday".

The correct sentences should be:

Thank you for your information. They will reply to us with the situation next Monday.

Thank you for your information. They will reply us next Monday.
(This may seem better.)

Thank you for your information. (The said party)'ll reply us the situation next Monday.