Welcome to the land of Linux
Endless OS is a nice, friendly introduction. My advice is think think of it more like Android for a PC, and less like Windows. Check out the App Center, that’s where you’ll find all the available apps and have a one-click install, just like on a phone.
Also get to know the keyboard shortcuts: Alt-Tab to switch windows (like on Windows) but also Alt-~ (tilde) to switch between windows of the same application, and Super-# (Super is the logo key) where # is the number of an application icon in your task bar. So Super-1 switches to the first one, Super-2 the second, and so on. Makes multi-tasking fast and easy.