FCPX space by moved clip is no longer automatically occupied by other clips

Cirlced in red is the indicator of the Position tool:

Either press A or use that little menu to choose the Select tool (a.k.a. "Arrow" tool).

You will have to manually delete the gap clips that were created while using the Position tool.

You have activated the Position tool.

Look in your screenshot the tailless arrow that is different from the usual arrow.

Press A to activate the usual Arrow tool.

The magnetic effect only works with the primary timeline.

You are probably moving clips connected to (above) the primary timeline.

If you have got another track above the main one you can make it magnetic by highlighting all of it, right-click on it and select "Create Storyline" from the contextual menu.

Max, you will likely find these free tutorials will save you lots of time learning FCP.

Steve at Ripple Training’s 60 minute FCP tutorial overview https://www.youtube.com/watch?v=HqUP7Zgeuck

Final Cut Bro getting started  https://youtu.be/L3bZ-ETKZ8U

Izzy Video tutorials. Older so the UI looks different but the concepts are still correct. https://youtu.be/_jvyrnQpR1E?list=PLp5SAgbM8S87n1qvv34-PAU2zMHLlXyfb