I would be very interested in any tips regarding improving one’s speech skills. I am way too prone to talking too fast to the point where I have sometimes trouble forming words and any like “I didn’t get that” makes me more anxious increasing my rate of mistakes.
But strangely it largely creeped up to me when I was around 20ish years old, while my teenage anxiety largely diminished.
I personally recommend joining a local Toastmasters club. They can help you with speed, tone, volume, etc. It can benefit your conversational speech as well, not only public speaking.
Or a local speech course. I took an eight-week course in public speaking in college, and it was probably the most useful course I took there. I can do talks in front of tech groups or hobby groups... not without some sweating, but still more effectively than most people.
Read and record yourself. Repeat until you learn what sounds good coming out of your mouth. Write at the same time. Think about your words. Savor both. It makes a world of difference. When you write read aloud.
Share. Communication of all kinds goes together. If you get this far you may also find that practicing your voice in speech and writing will improve your self confidence too.
There's a free short course on Udemy somewhere from Peter Barker who is a professional voice over artist. That's worth looking up - there's a section that covers correcting and improving a lot of common speech problems, from stuttering, talking too fast, mumbling, and how to improve the resonance of your voice. Might be worth a look.
But strangely it largely creeped up to me when I was around 20ish years old, while my teenage anxiety largely diminished.