Venus and moon sus behavior

Venus and moon sus behavior
„Time: 19:30
Location: Baden-Württemberg„
I (22/M)was driving home with my sister (27) around 19:30. And since its winter it was already dark at this time. We both noticed how a star near the moon was extremely bright. But it wasn’t pulsating so i was really sure it was a planet and not a star. So opened the app „Sky Guiding“ where i check always the planet and the stars. I directed the phone directly towards the moon and at that „ bright star“ but the app it wasn’t showing me that the moon is there. So i searched it manually the moon and it showed me, that at that time it was already under the horizon. But both me and my sister saw the moon above us. The app also showed us that the bright star is actually Venus. I didn’t think of it much and closed the app thinking it was a gps issue. 
And we were commenting how beautiful the Moon and Venus look like. And out of nowhere Venus dropped really low and it went back up at its original place. And we both noticed it. The moon stayed in same place. My sister said it was an airplane, but even an airplane canteen drop or fly that fast. It was link a blink. And kinda it looked like sky was lagging. Can someone help me get a better explanation of what i saw. Nothing adds up. Even chat gpt doesn’t make sense. It only made me sure that the app was right and the moon was under the horizon tonight.
If anyone has any further questions, im ready to answer them.