Petite Fleur additions / chords

I have learned the Petite Fleur composition by heart (clarinet) with a guitar accompaniment by a friend.
Some gifted/generous person added a section to the piece
(very welcome! reprinted in the "Query" file below in red with bits of the original Petite Fleur
on either side in black)
Alas, it is beyond me to add the missing chords to the red part.
I just do not know where to start even !!
Is there somebody capable of doing that, please ?1
Thank you ....
pískal

P.S. My interest is purely non commercial, playing the clarinet is my latest hobby;
I actually started 2 years ago, when I was 72 ..... and I am finding that sporting an Acker Bilk goatee
and wearing a bowler hat is sadly not enough !