For me, my social anxiety started to end after a bit of therapy, but also exposure as nso95 suggests. Like, if you put me in a crowded room with mostly people I didn't know I'd experience tunnel vision, couldn't make sense of all the sounds around me, and would be clinging to a wall. Starting with smaller groups (this was not entirely deliberate, it's just how it worked out), I got better at being around groups of people that I was unfamiliar with and interacting with them. Then some practice (forced by school) in public speaking helped me some more (small groups, just a class of 20-30 people, not hundreds).

For foreign language speaking, you just have to dive in at some point. You will say things wrong. You will find that you don't have the words. And this is fine! A major lesson for me was that everyone experiences this. No one is perfect (no matter how they seem), and if the fear is really fear of judgement, then they're jerks or bullies and you can ignore them. It's hard to internalize that, it was a long slog for me, but it's achievable. Practice, first, with people you trust or know, or with someone you find/hire online (there are services, but I don't recall any of them at the moment, that matchmake people with the language speakers they want).

From what I've learned on this journey, the nerves don't go away but the fear does. The most powerful thing you can do is to acknowledge that yes, you have this fear now but through time and practice, it can go away because it's mostly in your head. When presenting, most people do want to hear what you have to say. Nerves are a great thing because it lets you present at your very best - you just need to find your way to manage it.

You can start with baby steps - i.e. speaking up in meetings, presenting in smaller groups, etc. and then work your way up.

What I've also found useful for dealing with any situation that makes me feel uncomfortable is to question why it makes me feel uncomfortable. And the more uncomfortable I feel, the more I have to conquer it. Perhaps through an overarching goal of some sort.

For crowd talking or performance it helps if you practice your talk to someone you trust and can accept his criticism. Go through your presentation 3-4 times lets you memorize your presentation and distills your message. The familiar sentences will save you when anxiety hit you in the middle of the talk and you feel like your brain is empty. It also helps if you have a message instead of memorized sentences one after another - try to build your speech around one single message. If you present yourself in a foreign language the practice also helps finding the correct words and expressions.

It also helps if you image your audience naked.

The anxiety will maybe never go away but it can be familiar enough to become something you can always handle.

And remember - the only time a man can be brave is when he is afraid.

"I must not fear.

Fear is the mind-killer.

Fear is the little-death that brings total obliteration.

I will face my fear.

I will permit it to pass over me and through me.

And when it has gone past I will turn the inner eye to see its path.

Where the fear has gone there will be nothing. Only I will remain."

---

from Frank Herbert's Dune series.

Practise. Seek out opportunities to make these weaknesses your strengths. There's Toastmasters and other groups to help, lots of books.. but mainly, practise, do them over and over again. A lot of the great speakers of history were terrible in their youth, or stuttered, or something--a lot of people who achieve greatness made extra effort because it meant more to them than to other people. etc. Good luck!