When on Google, reset the zoom. Or at least look at it.

Reset the zoom?

Note that you need the correct version; most distros will list several versions which you must choose from based on the version of Chromium that Opera uses. That is the hard part.

What do you mean? Search results show in google.se, Opera's menus are in Swedish, websites tell you that you're in Sweden, ... there's about half a dozen ways I can interpret that and different ways to try to fix it.

The default setting is "Ask", as most people don't really want every website to know exactly where they are at all times. If you click on the badge (the lock or globe icon to the left of the address) you can access "site settings" and change it for that site to always allow - or always deny. Mind you, if you actually use a wired network your location can be several miles off.

I presume the description is for dark theme with private tabs? Dark theme is still something of a work in progress - previously it had no effect on private tabs (the background was always bright).

Item 2 is just how it works, unless you actually tell Opera to exit. On the "hamburger menu" there is a little icon that looks like the logo on a power button; if you click that a message will appear saying "All tabs will be closed" and then asking if you'd also like your history to be cleared,

Not sure why item 1 matters, as you can open a new speed dial tab at any time.

There is an old (based on Opera 12) mail program available, but it might as well be abandonware as they don't update it. I use it - have for years - but I really can't recommend it due to the lack of updates.

As that is a website you'd have to ask them, but start by making sure your language (in Settings) is set to English.

Mac is different, you have no idea what will happen in Windows.