I wrote a good code for simple movement but it still lagging

hello

I don't understand why simple movement need to lagging, even on powerful devices.

I made a simple game but it lags sometimes . I have written codes in the way that Godot and youtubers have mentioned documents.

I even use Smoothing- ddon from Lawnjelly. but steel lagging. the lagging be.

I can't put all the content of the whole game here so I just put a small example of movement script and simple images.

Please take a look if there's a mistake in the code or in the project settings, tell me.

The devices that I use: gaming pc, iphone 12 pro, and vivo. It would be worse if I recorded it. :(

I just want to use Godot for simple game not Unity, if there is no hope for this problem I have to go back to unity.

For reference, this was cross-posted on a GitHub issue: https://github.com/godotengine/godot/issues/59627