How to Create a International Multilingual Website?

How to create a international multilingual site?

This is a big question, I know. There are tons of answers out there but they are usually just fragments of plugins and solutions. So more specifically this is what I need to do.

Language Switcher
All Content is in multiple languages. A little language menu could switch the language. There are many plugins that seem to be able to do this. But which one will do the job well?

Each Language With Its Own URL
Each language has it’s own url or subdomain or directory (folder). Like https://www.example.es or es.example.com or www. example.com/es/. That might be done with the Host.

Visitors Language is Default
Visitors in each country gets the respective version of the site. French visitors get the French site by default. I know a simple javascript can determine what language the browser is using.

In Search Engine Results Internationally
Could the German version of the site show up in search engines in Germany. It seems Google only give you one country to market within. And do you have to be hosted in that country? I know Hungary only permits sites hosted in Hungary. So is there some way to have this one website show up on search engines in many countries?

All on 1 CMS?
Can all this be run from one WordPress CMS? Is it impossible? Can you run all these languages and show up on search engines throughout the world? Would it be better to divide it up and create separate sites hosted in their respective coutries? The website ranking and reputation would be best if the site was just one. Rather than scattered sites all over.

So do anybody has have ideas?

And here is the site. Micron Bio-Systems