"neither *I* nor the helpline will be available If there is anything you're already aware of that needs to be fixed... In American English we express the dates differently( Friday the 18th of April or Friday, April 18th), but I believe the form you used is considered correct in British English, although i'm not sure the comma is required.

Thank you, Chris, for your additional suggestions. Your'e right regarding the "before". The recipients have no public holiday on Friday, so with that mail I want to give them the chance to have results, needed on Friday, created before and also to ask me for organizing an on-call service for Friday if they mean to need one, but that also has to be done before Friday. So yes, I have to ask for "anyhing that needs to be fixed before ..."

Some other little things, more suggestions:

I want to inform you that due to
our (I would add that since you are talking about German specifically)

public holidays on Friday, 18th April, and on Monday, 21st April, neither I nor the helpline will be available.

If there is anything you're already aware of that needs to be fixed

before that period/date (I think you should use before, since you are not fixing it in the Easter period but before, right?)

please inform me
as soon as possible.
Thank you.



But off course Susan knows best since she is a native speaker.