How to repair hard drive?

An object weighing 5 kg fell on my laptop (everything is true), precisely at the point where the HDD is. Now when I start the laptop I only see a black picture and the HDD rattles. Can I fix it?

No, it is almost certainly broken and then no longer repairable. Install a new hard disk, install the operating system and restore data from the backup.

You can try to save the device with a different hard drive, but there's also a good chance that the circuit board or other components have been affected.

Switch off the laptop, do not try to switch it on again.

Depending on how important your data is to you, you are welcome to hire a professional data recovery company. The top dog is likely to be the Kroll-Ontrack company. Here you should reserve 1000 euro in your mind. They are not cheap.

Is worth a lot. Photos and files are backed up online. Only apps and games are gone. (I can always reinstall.)

Then forget the hard drive! Rescue attempts will be futile.

Can I plug in an old, unused 500GB HDD? Also SATA 2'5

It can't be repaired, sorry. But new HDDs don't cost the world, just look for 2.5 inch HDD hard drives

This is a total loss for a private user. There are special companies (or police authorities and secret services) that can open the HDD and read the data from the disks. Success is not certain, however, data loss is still possible and the costs are likely to be in the thousands.

The thing is that if really NOTHING is displayed, then almost certainly more than the HDD is broken