[Kazuki Araya]

Are the latest drivers Installed for both the video and sound card? Is "streaming" fine for other devices on the same network?

Yes. I already install the latest version for both video and sound card on my uncle laptop.
streaming online also no sound and slow motion playback video.

It may well be a hardware Issue, as a consequence of the said repair.

Are other devices on the same network streaming fine? To eliminate the probability of anything software-related, hit a clean Installation of Windows with only the bare essentials Installed thereafter. If It's still the same, take It back to the person(s) who're responsible for the damage.

Just now , im contacting the person in-charge of repair this laptop. But still no reply from they.