Greetings!
I have problem with adding keyframes. When I want to add one by rightclicking the timeline this appears.

I don't know why is that. Can I somehow add a keyframe? I tried "Keyframes" > "Insert Keyframe L/R" but that doesn't seem to work properly. When I add layers the just don't clip to any frame. I just wanted to make a simple light appearing and fading animation, changing opacity smoothly would be enough but I can't find any way to make it work. Can I please get some help?

You can just use the "Create Blank Frame" option in your image. We need to revise our wordings or change things up a bit, because that option actually creates a blank one.

blacklenk wrote:I just wanted to make a simple light appearing and fading animation, changing opacity smoothly would be enough but I can't find any way to make it work.

Currently, the only way to insert opacity keyframes is through the Animation docker. There is a triangle next to the new keyframe button (top left button in the group of six at the bottom) which gives you a popup menu. Once you have created the keyframe, you can adjust its opacity value through the layer opacity slider or the animation curves docker.