This is a very common question to developers who want to learn a new language or newbies who are just starting out in their programming journey. For me, I would advice you understand the approach you want to take. There several ways to develop android apps: native, hybrid, or even mobile web. All these approaches have their different development environments and tools you have to set up. They all have their individual learning curves, especially for newbies. But hybrid apps may be easier for someone who is already a developer on the web stack. Personally, I prefer the native route and I do a lot of native android development.
So after getting a grasp of what approach and tool you want to employ for your development, then take a small project and work on. Overtime I have observed that just watching online courses without having a project to work on is a mere waist of time. Its's best to learn by doing. So pick a small project or one you have done in another language and rewrite it in android. Download the necessary development environment, setup and go through the 'getting started' section on android development website. You are good to go.
Google, in collaboration with Udemy, has developed great courses for beginners, developers, and even advanced android courses that are free online. Please see the link below.