Laptop does not work as before, what can I do as a layman?

I have a laptop from Medion. I have also been very satisfied. He always worked flawlessly until I took him to university with me in my backpack.
Since then he works only slowly.
What can I do? Is the hard drive broken?
So far, I've done a rollback to previous days and uninstalled superfluous programs, but to no avail

Would be glad about your advice.

I would defragment him once, if he still did not go I would reset him.

Edit: Could be synonymous a hardware error, but I would send him for repair

No matter what you do, make a backup first.

I do not see Paula's answer with defragmenting that way.
So much does a defragmented HDD not press on the power brake - at least not if the HDD is not proppevoll.

However, a defective HDD can go strong and even fail at short notice (hence the backup!).

Install the https://crystalmark.info/en/ and check the health of your HDD.

Unfortunately, by resetting your laptop, you effectively destroyed all the analytic data that could have been used to derive something.

Note: Reset usually does not solve any problems. We're no longer on Windows 95, where that was the case. It only creates the feeling (!) Of a new, clean Windows. (Whatever that may be, once you have all the programs installed again…)

Maybe a Ram has relaxed.

Before I could start the installation everything started to work again. Miraculously, the speed / performance has risen again. I will observe this for the next few days, if I notice changes, I will install the program recommended by you.