“put it down”
Put down means to place something you are holding on a surface. With a phone, it also suggests stopping looking at it or setting it aside.
A2-35 / CEFR A2 / EPISODE 35
Discussing time spent on a phone
SceneAt night in Tina's room. She is absorbed in her phone.

WORDS & CONTEXT
Put down means to place something you are holding on a surface. With a phone, it also suggests stopping looking at it or setting it aside.
Gimme is a casual pronunciation of give me, the same kind of contraction as gotta (A2-24) and gonna (A2-04). It is used in conversation between friends; in writing, use give me. Here it means "Name one."
Here Why don't you ...? does not blame someone for not doing something; it suggests trying it: "Why not ...?" Autoplay means videos playing automatically, and turn off means to switch off. The line does not give the actual steps in the app.
As a verb, film means to record video. This time Frank filmed only the rock and the egg, with neither his face nor his voice. Because it was made differently from his science video in A2-31, which shows his face and has his voice, Tina did not recognize the creator. They are talking about one video; it does not mean Tina spent all three hours watching Frank's videos.
Stop ...ing means to quit doing something, and can't stop ...ing means to be unable to quit. Videos I can't stop watching means videos Tina cannot stop watching. Tina jokingly protests after learning that Frank, who told her to put her phone down, is the one making videos she can't stop watching. The punchline also works as a compliment: the video was good.