There are few tweakscan be done via easy method or advanced method, depending on the user's capability. The easier method is via downloading Windows Blinds application and make changes from there (remember Windows Blinds is NOT FREE). On the other side is by using Open Shell tool via github.com .. Otherwise via registry tweaking method (which brings back Windows Classic look-a-like) for advanced users which is harder way.
to solely put the Windows 11 taskbar to the left (thus opening the startmenu to the left), see here: www.makeuseof.com
Openshell is very nice for the Start menu (the vertical menu above the start button). It's like Windows 10; instructions how to use it are here: www.makeuseof.com
But many also want the old taskbar back (the horizontal icons at the bottom). The best way to do that is to install "Explorer Patcher" (github.com); click on "ep_setup" under the latetest version to download ! When installed you can acces the options by rightclicking an empty space on the taskbar and chose "Properties".
It has a lot of options, which are explained in detail here: allthings.how
And finally, if you also want vertical menus on your taskbar icons (submenus for your taskbar icons), there is "TrueLaunchBar": www.truelaunchbar.com (It only works, when you installed "Explorer Patcher" before).