To translate static strings, go to the String Translation section of the WPML plugin.
You will get to this page:
Click on the + sign and add a translation to these words.
This is how it will look on the translation of the Popular Courses widget:
To translate the login and registration forms, you need to turn on Auto registering strings for translation in the String translations section. Check the box and click Edit.
Choose domains for auto-registering strings and click Apply.
You can find the necessary string to translate within the list or make a search based on the keywords.
That is how the list of the strings will look after making a search based on a keyword:
Click on the + and add a translation.
Add translation to all the fields available in the login and registration forms.
This is how it will look:
