I just realized (to late) that the conmigo app has no export feature.
This is especially bad because its settle algorithm isn’t really good.
But IT is simple, so here is how you get the data out:

1. Copy the conmigo database (conmigo.db, usually located in /data/data/com.conmigo.share/) onto a PC with Firefox. I used root explorer and mailed me the file.
2. Install Firefox extension sqlite manager (from https://addons.mozilla.org/de/firefox/addon/sqlite-manager/)
3. Start it via Extras->SQLite Manager
4. Open the database in sqlite manager
5. Run the following SQL. There should be a tab for running SQL:
SELECT 'transaction'.'date',
'transaction'.'description',
'transaction'.'amount',
'from'.'nickname' as 'from',
'for'.'nickname' as 'for',
'transaction_participant'.'participant_amount'
FROM 'transaction'
JOIN 'transaction_owner'
ON 'transaction_owner'.'transaction_id' = 'transaction'.'id'
JOIN 'transaction_participant'
ON 'transaction_participant'.'transaction_id' = 'transaction'.'id'
JOIN 'user' 'from'
ON 'transaction_owner'.'user_id' = 'from'.'id'
JOIN 'user' 'for'
ON 'transaction_participant'.'user_id' = 'for'.'id'
where 'transaction_participant'.'participant_amount' > 0
order by date asc

6. Make sure  to run it exactly like this, with all ‘ correctly in place.
7. Select the result table and copy it to csv (right click)

Note that this works for the current version 2.0. Might get broken in later versions.