I cannot open Android Studio
The tutorial you linked to never mentions Android Studio. In fact, it is not a tutorial about installing the Android Studio IDE. It is a tutorial about installing the Android SDK which you can use to run Android AVDs.
to get to Android Device Manager
You do not need Android Studio (the IDE) to run the Device Manager. The device manager can be opened through the SDK Manager by running the
android executable, which is located in the directory where you installed the SDK.
According to the tutorial, you installed it into:
(There is an error on step 3 in the tutorial which mentions
/android-sdk-linux/tools instead, but whatever)
For this reason, you will be able to run the SDK Manager like this:
When the SDK Manager opens, use the menu:
Tools → Manage AVDs...
Create one or more AVDs and then run them. You should definitely choose to create them with x86 ABI, because those using the ARM architecture will be very slow since the CPU needs to be emulated.
The system images for Android must be installed through the SDK Manager that you opened before. You need to close the AVD Manager to use the SDK Manager.