German Authorised Service Provider required money for mythical damages with mythical liquid

[Alyonuschka]

Please help me with advice,
my laptop did not turn on,
after sending to German Authorised Service Provider from HP , on the 8th day they has writed to me about a lot of damages with unknow liquid, although during 7 days before they could not find any traces from the unknown liquid,
i am sure, that before i had sending the laptop to ASP from HP there was not any liquid damage.
and the fact that 7 days the technician did not see any traces of liquid and on the 8th. they have writed about a lot of damages : Motherboard, LCD cabel, touchpoint, keyboard(this is important) with traces of liquid damages.
Yesterday i found out, that technician had changed the keyboard from the laptop with issue withkeyboard from the laptop that belong to my assistant. and before the laptop with issue was sent both keyboards were functioning.
And this message about not functioning, with liquid damages keyboard .
First,
Keyboard that was installed on another laptop that works good, with both of keyboards,
Second,
on the keyboard, that was send unlikely with broken laptop, was found the same liquid, that had damaged Mainboard ans lot of internal devices, but the keyboard belongs to another laptop other user, and was functioning before delivery to Service Provider,
third ,
i have at the moment the keyboard that belongs really to broken laptop and i am ready to provide it to check whether the keyboard has the traces of any liquids, but i am sure there is not any .
i could assert that the laptop had not any liquids damages before it was sent,
i could assert that if there iare any liquid damages at the moment any liquid traces on the mainboard , that was done by the Service Provider,
i have tried to speak with American Support but they interrupted my story and dropped connection,
i am ready to hear any advices and thoughts,
thank you a lot,
sincerely,
Alyonuschka

[Alyonuschka]

p.s. 

To all my asks to provide the photos  was received the answer: " sorry , corrupted connection, we shall try tomorrow again"

[Alyonuschka]

it takes about week to "find" the mythical liquid, during the week i was at least least 2 times called , and after 5 days with question , whether they might to install Operation System , because they could not find any cause of the issue , 3 days before was found the mithycal liquid, that were caused the issue with my laptop(do not turn on).