Navigation and movement at the very beginning of the game (tutorial?) is extremely confusing! I'm playing RPGs since decades, but such a confusion never happened! I don't know how to move and automatically follow my character so that it is always visible..

What does "cross-save" and "is being uploaded" in the save or laod panel mean?
I do not want to upload my save games anywhere, because I manage my backups by myself.How can I disable that?

You can rotate and pan the camera around, but I think it has to be done manually. One of the keys - I forget which - will re-center the screen on your character, but you still may need to rotate it around to see properly. (DEL and END are the keys to rotate the camera view left and right, respectively.)

Cross-save, and upload, is just a "cloud save" option. That way, if you play on more than one computer - your saves will be accessible to you on all of them. Also, if your computer completely dies, your saves won't be lost.

Just don't start the game via the Larian launcher. Instead of the shortcut's default target path \Baldurs Gate 3\Launcher\LariLauncher.exe set it to \Baldurs Gate 3\bin\bg3.exe for Vulkan or \Baldurs Gate 3\bin\bg3_dx11 for DirectX11.

That will of course also deny Larian to track your gameplay statistics. So maybe just ignore it? That one is fairly simple. From the first moment on the camera will follow your character until you start moving the camera freely (edge panning or keyboard controls). To follow your character's movement once again simply double click the portrait. This works in bird's-eye view too (if you didn't know that existed: you can toggle it with "o")