Good posture also helps you breathe better, which can help you feel more energized and concentrate better. Your diaphragm doesn’t work right when you sit hunched over, so your breath gets more shallow.
If you ever need to talk a lot for work or some other reason, good posture is essential so your voice sounds good and doesn’t get tired too easily.
And it helps strengthen your core, which is good for balance and other things.
You can think of “le” as a way of showing that it’s a syllabic L. Meaning that you say a dark L, and there isn’t really a vowel before it. The L takes up the whole syllable. It can sound like there’s a schwa in there (usually just a blip of one), but that’s just part of how you say the dark L. It comes from having the back part of your tongue press down and back.
This happens at the end of a word when the L is in an unstressed syllable. The spelling can vary a little. For example:
There isn’t really a reason why the spelling is different. That’s just how it happened to develop.
The pronunciation can vary a little too. If you hold the L longer, or emphasize the syllable more, it can sound more like a proper vowel is in there. But your tongue stays a tiny bit lower than it does for the schwa sounds.