It used to take several contributed modules to make even a small multi-lingual Drupal 7 site. Now, you can translate everything using just the Drupal 8 core.
Step 1: Enable the translation modules
You need to enable these four core Drupal modules in order to translate your site.

Step 2: Translate the Drupal core
First, let's translate of the core language inside the Drupal. In this example, I'm going to add Spanish as an option on my site:
Go to Configuration > Languages
Click "Add language"
Choose your language and click "Add language".
Click on the percentage area, under "Interface Translation".
You'll be able to search for and manually translate all the language strings in here:
Step 3: Translate your own site set-up
Go to Structure > Content types, you'll see a "Translate" option for your content types:

Inside the next screen, you'll see similar "Translate" links for all your fields:

Step 4: Add content
Now we can add content to your Drupal site.
- Go to Configuration > Content language and translation.
- Click the box next to "Content":

Note: This is an important step as you can set a specific translation for your content type. That means, the content type default language will be set to a particular language(like German).

After this step, all content of "Biography" type will be by default translated to german.