How do I know if I will reach my investment goal?

The app continuously calculates whether you are on track. Based on your current capital, expected returns and the time remaining, you see how likely it is that you will reach your goal.

If you fall behind, you get a notification with concrete suggestions: raise your monthly contribution, adjust your target amount or move your end date. So you don't have to do the maths yourself. More on the approach at goal-based investing.