If you change without interruption (e.g. stop overs that take less than 20-30 minutes) from one line to another, you will not be required to check-out. The app will recognize that you changed line and calculate the optimal fare.
For longer interruptions, we recommend a temporary check-out. When you resume your journey, simply check-in again. This has no influence on the calculation of the price. The system calculates automatically all journeys and computes the cheapest ticket combination possible.