Windows OS residing in `/dev/sda5` in the figure you've shown. In your system it's the only `ntfs` partition large enough to hold windows installation.

You can easily mount and see which partition containing what and decide to remove them. Like in Windows installation partition you'll find folders relevant to windows. To mount `ntfs` file system in Linux you need `ntfs-3g` driver, which usually comes inbuilt with Ubuntu. Otherwise install it using `apt install ntfs-3g`.

In your system `/dev/sda1` is mounted as `/boot/efi`. So, it's containing `grub` boot loader. So, don't delete it even by mistake. You can delete `/dev/sda2-/dev/sda5` and `sda6, sda7`.

If your main purpose is freeing up disk space I'll suggest you to delete `/dev/sda5` only. Other partitions mentioned above has windows recovery, Windows bootloader etc. They may be helpful in case of a factory restore etc.

Always have a backup of all necessary files before deleting anything.