laptop display problem

[Garibolz]

After a month of not using the computer, I turn on it and it works only if it is connected to an external monitor. Without the external monitor, the colors of the display become or white or purple and the mouse works very badly, it moves after one minute more or less.
For me, some cables that connect the computer to its own display are ruined. But I don't understand how one month of inactivity can cause it, and I don't know how to fix it and how much it could cost.

[WAWood]

@Garibolz 

You failed to provide any model number and you say this is a laptop -- but then you mention display cables.

So, did you take this apart to check out the ribbon cables?

[Garibolz]

When I wrote the message I didn't have my computer with me, so I only wrote the general PC model. If the precise model is necessary I will write it. My idea is open the laptop and check if the connection cable has some problem. So I could buy another cable and solve the problem with a few Euros, yesterday I looked for the cable on Amazon. I haven’t opened the computer yet because I’m afraid to mess up.