Questionable HP Technical Service support

[Waan]

I got this laptop in 2019 before I went to Germany for my education. I had a boot up problem (it simply wouldn't turn on) within my warranty period and seeked help from HP service support (in Germany, as it had international warranty). After some cumbersome phone-guided efforts of troubleshooting procedure, they analysed it to be Battery-Charger related. They sent a new power cable charger/adaptor to fix the issue. It didn't work, the device wouldn't still turn on. After which, they had it picked up by UPS for looking into it. Later they told that the system couldn't be fixed due to faulty motherboard , thereby claiming a replacement under warranty isn't applicable as it seemed to them that water has entered into it (which I didn't accept, as.. to my knowledge- I was pretty sure that nothing of that sorts could have even remotely occured). Therefore, I had no other choice than to let it go and purchase another device for my needs. Later  when I returned back after my education (2023) I was curious to check if it could be fixed, therefore i sought the help of a local vendor and to my surprise, they called me back in a couple of hours to notify that the system has been rectified and that some 'RTC Chip' was faulty and it was replaced for a price (which could have been free if it was rectified when my warranty was still valid) I had to endure through the efforts of fixing this since I really wanted it to work. It boots up now, but I am in need of an OS since it was wiped out clear when I first sent it to HP. 

I kindly request HP Technical Team to help me with this problem.

Thanks in advance