My original 3DS is unresponsive

I’ll start by stating that I’m new to all of this and, while I really want to start fixing various of my old devices, I don’t have a lot of experience.
So to the problem itself. My 3DS is unresponsive to my inputs, meaning that while the console turns on and reads games fine, I can’t control what happens in the device. It just starts moving everywhere and opening apps, without any input whatsoever. I tried cleaning the touchscreen, with isopropyl alcohol, and the buttons as well, from the outside but nothing happened.
I have never opened a 3DS before, but I can figure it out with a guide, the problem is I don’t know what I’ll be looking for once it’s opened, nor what is doing this.
Also, the 3DS was working fine, until it started spazzing out like I mentioned out of seemingly, nowhere.
Finally the 3DS is from Europe so I don’t know if that affects the solution to my problem?
Can someone help me?

first determine if it’s the digitizer at fault or the buttons - you may be able to do this if there is a touch calibration mode and see if it’s registering false inputs, if no, or if you can’t gain acess to the mode then disconnect the digitizer ribbon and if the problem persists then you know it’s likely down to the physical buttons.

If it’s the physical buttons, then afair most of the buttons on 3DS are all tactile dome buttons, meaning you’ll likely (if they’re anything like PSP but someone correct me if I’m wrong) peel off the sticker holding them over the board and clean off whatever is causing your ghost inputs, 70/30 IPA/deinozied water would be my go to for this. You may also have to polish the inside of the domes if they are tarnished.