Boot problems?

For experimental reasons I made Kali linux as a dual boot with Win10 on my laptop (HP Elitebook 820 G2). I was unable to access Windows after installing Kali Linux. I ignored that and used Kali Linux as my operating system. Now I would like to go back to Windows 10. I can't boot Windows 10 as I said. But there are Windows files on the SSD. Actually everything is there. But I can't access it. What can I do to get back to Windows 10?

thanks

Reredderr

(Note: I don't want to hear here that Kali Linux is a distro for pros and that it is bad for a beginner to get it.)

Did you back up the Windows boot partition beforehand? Backups are a great invention.

You can run the recovery functions from a Windows boot stick, which do not create the boot sector.

Ah ok and this stick I create with another win 10 PC right?

Yes.

Backups work wonderfully with CloneZilla. If you're experimenting with Linux, there would be a useful tool.