I wanted to install Windows on my Ubuntu laptop, but inadvertently only formatted part of the hard drive, what now?

I have a huge problem, I wanted to switch from Ubuntu to Windows on my computer, then the stick for booting Windows told me that it couldn't be loaded onto the hard drive, so I could log back into Ubuntu, where I was only able to do two small parts Reformat the hard drive to NTFs, thought that it might work, restarted the laptop, but now I can neither boot it up on Ubuntu nor install Windows, how can I solve this problem?

I'm desperate, thanks for every tip!

Do you have access to another computer or is there maybe a Linux Live CD that you could boot from? I would then simply delete all partitions with gParted and then let Windows create new ones.

Sounds very promising, so I should try reinstalling Linux, then delete the partitions with this program gParted and then install Windows? I'm not sure if I can install Linux at all, since I'm part of the hard drive NTFs should work anyway?

The operating system can be started directly from the CD from a Linux Live CD without having to install it separately. You then simply delete all partitions with gParted and then install Windows.