Which sites improve my speaking skills?
There's a worldwide organization called Toastmasters International -Home
They're everywhere and I'd bet a chapter is fairly close to where you live.
The cost every six months is minimal and you'll learn a plethora of skills usually at a once a week meeting. Online is a lousy way to brush up on speaking because there's much more to talking than simply talking. There's body language too along with knowing when to not speak. There's knowing how to act and react in front audience. There's also necessary practice needed so one can get their idea across in a limited amount of time. No one wants to hear someone blithering away while not getting to the point.
You'll receive (and give) advice to others. We can often be unaware of certain phrases and speech patterns we repeat too much, so getting (and yes, giving) positive criticism is an absolute must. This is true for even the most polished of public speakers.
Good luck on your journey!