Help deal with the analysis of the parties in Lichess and export them from there.

Hello!
Help deal with the analysis of the parties in Lichess and export them from there.
Here I am analyzing the game according to the book of Averbach, how can I then export this analysis in PGN format with all the branches and options, such as on move 9? (a photo)
http://prntscr.com/m4wlvb
Below, under the board, you can see moves in a separate box in the PGN frame, but for some reason without variations, only the main line. When you click the "Import to PGN" button, nothing happens at all. (a photo)
http://prntscr.com/m4wms0
Ps / What is a FEN code and what can I use it for?
Thank!

If you want to capture variations, first thing that comes to mind is inputting the moves in a chapter of a Study:
lichess.org/study

When you're finished, you can export the PGN by going to the "Share & export" tab below the board and choosing "Chapter PGN"
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"Import PGN" imports a game into the analysis board from a PGN that you can paste in the PGN field. If you were to click on it before pasting a PGN, you'd be attempting to import a PGN that was already there.
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FEN is notation that can be used to describe any chess position. It's actually pretty easy to read, but you'll generally use it by taking any given position, like one from a game, and inputting it to, for example, a "from position" game or to the analysis board.