U koliko sati se nađemo? means “What time shall we meet?”
You ask the question on the underground – the underground (U-Bahn in German) gives you the u. The person is wearing the same expensive watch as in the first video, on the left and slightly odd, and has the well-fed tiger with them: koliko sati. You suggest meeting in the evening at the lake where somebody plays the harpsichord at night and the moon comes up. Lake, night, harpsichord and moon give you se nađemo.
That lets you arrange to meet. The times themselves come in the next two videos.