Behind the mechanical keyboard is a sheet of frosted plastic which embedded within it are a collection of tiny LED’s which hopefully illuminate the sheet evenly that then passes the light outwards thru holes in the mechanical keyboard into the discrete key and the letter or symbols are lit.

So … a liquid spill can affect this sheet with a deposit of material which light is prevented from exiting outwards. It’s also possible one or more LED’s have failed as well.

So to gain access to the sheet one needs to remove the logic board as we don’t have a guide for you system you’ll need to follow as best as you can this guide MacBook Pro 13" Touch Bar 2019 Logic board Replacement there are differences but it’s very close to the same process.

Now looking at the upper case we see a sizable black sheet covering the keyboard area, carefully unglue the edge and the keyboard cable which passes through it, you should then be able to lift it out this assembly this is the backlight unit. If you just had a spill then cleaning the other side should remove what is blocking of the light, otherwise you’ll need to replace it.

This is where things get costly! As Apple doesn’t offer the sheet as a replaceable SKU. You might find it offered as a used part where someone has parted out a system, otherwise it’s a new upper case assembly! MacBook Pro 13" (A2289, A2338, 2020) Upper Case Assembly

Here’s a better image on the cable end

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@plushar123 since this "by holding my finger there it fixes it" removes those lines it stands to reason that you will need either a new cable or a new connector. Check the contacts to make sure that none of them is bend etc. Clean the cable end contacts with something like a hard pencil eraser or even some scrub pad.

We might get a better idea if you post some pictures of the cable ends as well as the actual connector. Looks like the LCD and touch controller cable are one. Check the Lenovo X1 Tablet Gen3 Hardware Maintenance Manual page 70. It is definitely easier to replace the cable then the connector. I would opt for that.

Adding images to an existing question

@plushar123 something looks weird on the cable. Could just be my old eyes. Check the area marked and/or post a close-up image.

So I bought a lenovo tablet for dirt cheap and I'm trying to fix it. I think it's from either the cable or the connector on the lcd screen. Both cable and connector look fine. I've opened the device and apply pressure where connector and cable meet and by holding my finger there it fixes it. I have cleaned both connector and the cable with isopropyl alcohol and it's still the same. The line are mostly red sometimes green and cover the whole screen. Touchscreen still works fine and so are the speakers. And this happens sometimes. The lcd flickering usually happens when my tablet is being moved.