Robotic tests should be independent

So i recently started using Robotium for the first time and noticed after some time that they are Executed in an alphabetical order. This made some test not work, because i needed the "introduction" of my app to be finished and than start other tests.

Since i have never used Automated tests before, im not sure how to write the tests right now. Should all the test cases ALWAYS be independent from each other?

This would mean in my case, that the flag for the introduction should be set false for some tests and true for other tests programmatically.

Or is it also right to assume that one test case has been Executed before another one?