Calc: How can I merge every nth line with a previous line?

I have a spreadsheet where each cell contains multiple key value pairs. Every value is on a new line. The content of every cell iis the following: image description.
I need to somehow merge the every second line in the cell with the previous line, so that every key value pair would be in a single line: image description
How can I do that? I tried to match new line character with a regex and replace it with a space, but it merges every line in a cell into one line: image description

Test file to play with.

Find: ([^\n]+)\n([^\n]+)

Replace: $1 $2


Thank you!

Multiline cells should generally be avoided.
See also this example: ask251055reorgaizingMultilineCells_1.ods.

Thank you for the example file!