Hi. I am a newish linux user and have just installed the Debian 11 stable with kde plasma 5.20.5 on my lenovo ideapad ( i3-6006U) and integrated intel graphics.

I have installed debian separately in a 25GB partition so that I don't wipe out all my docs if I want to change my distro or if I mess something up while tinkering with my system.

Now the problem is that I have two separate partitions in my hard drive which I use to store my data. Now, i can read the data in my drive, however, I can't delete or paste anything in it. I can download some files to the partition, but i can't delete them after.

Previously on Linux mint XFCE, I just changed the permissions in the file manager for my partitions in root mode to read and write, and it worked well after a reboot.

But I can't find the open as root option in the dolphin file manager. Neither do the addons for getting that option work (It asks for the root password, but the window with root privilege does not open after I enter the root password).

I also tried to make a directory in the partition using terminal with root privilege but it gives me an error saying the partition is read only.

But when I look at the permissions for the partition using the file manager, it shows that my user is the owner, and the owner can view and modify content.

Now, I have been using debian and KDE for a week or so, and I don't want to distrohop for something which I feel is a trivial issue but is bugging me because I am new to it. Also KDE is starting to grow on me. Any help?

Since you're using a rather old version of plasma, your best option is to install the "open as root" service menu. Can be done in several ways.
1) open dolphin>settings>configure dolphin>contextmenu>get more
2) download the file manually and put it in ~/.local/share/kservices5/ServiceMenus https://store.kde.org/p/1384645/

https://imgur.com/a/181PmpB

Ps: since you're new to the game. The previous post is how to get some extra service menus in dolphin and in most cases ( unless it requires an install script first, for example) it works by the same principle. It's a bit like Nemo's custom actions and scripts, but more advanced. If you look on the kde store under section service menus you'll find a ton of them.https://store.kde.org/browse?cat=102&ord=rating. I strongly suggest you take a good look around ( sort by rating is a good idea) before you install any.
Once you know how it works, you can make them yourself. Pretty much anything you want really. Here are a few examples:https://imgur.com/a/8QZlNcy

So, that particular stuff will reside in either ~/.local/share/kservices5 or ~/.local/share/kservices5/ServiceMenus. They can be straightforward or they can exec a script or a key emulator, whatever.For example, a service menu to toggle a tiled layout:https://imgur.com/a/uABqER3