Question: The upper content in the webpage covers the lower content when screen size is shrinked. What might be the solution to this problem? Is'nt the lower content supposed to move down accordingly?

Answer: 
While not officially documented (yet), flatten() also exists as a built-in formula.
See [here for more info](https://infoinspired.com/google-docs/spreadsheet/flatten-function-in-google-sheets/#:%7E:text=The%20purpose%20of%20the%20FLATTEN,separate%20rows%20in%20a%20column.).

[![Example](https://i.stack.imgur.com/0HN4t.png)](https://i.stack.imgur.com/0HN4t.png)

UPDATE: Since the end of 2020 the function is now documented. See [here](https://support.google.com/docs/answer/10307761?hl=en) for more info.
Thanks to JPV and based on his answer, I added `FILTER` to leave out empty cells:

```
=FILTER(FLATTEN(B2:L7), FLATTEN(B2:L7)<>"")

```

Plus `TRANSPOSE`, I didn't specify this but I wanted multiple *columns* into one, not multiple *rows* into 1 column.

```
=FILTER(FLATTEN(TRANSPOSE(B2:L7)), FLATTEN(TRANSPOSE(B2:L7))<>"")

```