You can set up your own home page or pages in the browser, so that when the browser opens, it opens there. Just press Alt P to go to Settings (or click on the Opera logo to the upper left of the browser to access the main menu, and then click on Settings), and for the On Startup Item, near the top, you can select Open a Specific Page or set of Pages. That seems to be what you would like to do. Click on Set Pages there, and you are good to go.
Now for your new tab page, you will get the Speed Dial. However if you don't want it, you can download the extension from the Opera Store called Custom New Page, https://addons.opera.com/en/extensions/details/custom-new-tab-page/?display=en
and set your own new tab page.
In case you ever want to go to the Speed Dial with the above settings you can click on the 8 small sqaures to the left of the Address Bar, and that will take you there.
On the Menu items, you get them by clicking on that Opera Logo on the upper left side of the browser. Now there are many keyboard shortcuts there, so after a while, you can access quickly quite a few of the items. Like settings/Alt P, your list of extensions, Ctrl Shift E, and others, History Ctrl H, new tabs, Ctrl T, etc.
Press F1 and you get the Help menu (you can also access it by clicking on the Opera Menu, and Help is one of the items). That help menu is a FAQ with a lot of subject areas that are discussed.