Franbern, every time you close the site/app to check your email for a verification code or password link, you will need to start the login process again. If you are having to close something down so you can look at your email, it sounds as if you are not yet comfortable about moving between open apps. In Windows 10, you can see small images of all open apps by selecting the 'task view' button. You can click the app you want to see full screen, select 'task view' again and pick another, no closing anything in between. You can copy and paste between them too. You can also close them down in 'task view'. If you can't find 'task view' after hovering the cursor over all the symbols along the bottom of your screen you may have to search your Windows 10 PC or Google it to see what it looks like.
If you want to move between internet pages (and not shut one down in order to open another), you can do the same by opening new tabs (little + sign to the right of the top of the page you have open). To close a tab, click the x in the corner.
Pardon me if you already know all this but your description leads me to think you may not and I meet many people who have not found out (or been shown) how to move between open screens, apps and web pages on a PC, tablet or smartphone.
Angela Rayner lashes out and calls Sunak “pint sized loser”.