How do I fix the lag in my game?

I’m quite new to GDevelop and game making in general, but I’m making a vertical platformer which is quite tall at this point (around 4000 pixels in height) and I’ve come to notice that the game slows down quite a bit when I preview it. Whether that’s because it’s loading everything all at once or something else. I’m wondering if there is a way to avoid this by not loading everything at once for example.
Because I was wanting to double the height of the game, I was just a bit concerned that it may effect the game if I don’t fix it.