I started learning french in german. Than I started learning Navajo. It ist only available in english. And now my savings in french are gone. And it is english as well. Which is not the problem. But I have to start from the beginning!
Adding languages will not make you lose progress in existing courses. You can switch between courses you’ve started by clicking on the flag icon in the top right corner of Duolingo and selecting a different flag from the drop-down menu.
Sometimes you have to tap [+Add a course] or [... more] to see the courses from another base language.