In this tutorial im going to solve above mentioned issues.

Error:-

Android sdkmanager not found. Update to the latest Android SDK and ensure that the cmdline-tools are installed to resolve this.

Solution:-

Just like you, I have Android Studio installed, the key is to install Android SDK Command-line Tools, steps being:

1. Open Android Studio
2. In the Menu bar , click Tools(4th last)
3. choose SDK Tools panel
4. Tick Android SDK Command-line Tools
5. Click Apply at bottom of the window

Next click on apply button then then download successfully.