Hello Krisztian

In Windows an image can be rotated and saved.

The image can then have an information that says how (in degrees) much the image should be rotated when viewed.

Servers does (normally) not use this information and therefore an image will be shown as it was originally oriented.

What to do then?

You open the image in a tool like the free and good IrfanView.

In here you rotate the image and then remember to save the image.

The image will be saved as it was rotated when you saved it, and the orientation will be shown as "normal" instead of a number of degrees.

It is this newly saved image you should use and upload to your server.