need some help guys

What is the problem? That the borders don't fit?

I THINK the problem here might be that your image varies so much from one side to another. You have too much light on one side and dark on the other. When you butt them together the contrast is pretty obvious. I don't know that there is anything that can be done for that beyond using a different image however.

If the borders are the problem, you either have to really make them fit to the other side everywhere or you have to find a texture which already meets this requirement.
Modifying the original texture should be a good solution, though the texture is not so high-resoluted. But for my pc, better textures would already be a problem I guess

It's basically as @Ruxandra and @Meltron said, if you want to replace these textures, you have to make sure that they are "seamless", otherwise you will see those rough borders There are quite a lot of tutorials available in the net about how to create seamless textures.

Yeah as an artist you can find methods to making textures but best way is to find a guide to making one.
To give a brief description is you create an image then cut in the center by four Then you put each of those four centers onto the four corners then your texture will match up onto each inter connecting one. But you will then have a center that has to be blended or fixed to get rid of it's problems.

Go onto youtube I am sure you can find someone doing that.

If I were you, I would use Krita since it's free AND has a tile feature (Press W key) which you can use to make seamless textures. Oh and paint.net (which is also free btw) has dds support built in. I'm using Krita for the tileable textures, and paint.net for both tileable textures and all the other textures. Krita doesn't have dds support though, so I bring it into paint.net and it works fine.