Received payment from Transferwise / First Declaration etc

I have received my first payment through my Transferwise GBP account from a UK client - 600 GBP. I have then sent this money to a french EUR bank account dedicated for business only.

Date of invoice to client: 24 July
Date of payment UK client to TW GBP account: 14 Aug

Date of payment sent from TW GBP account to French EUR bank account: 5 Sept
with balance transfer fees : 2.78 GBP and rate 1.11130 (0.8995)

I will receive 663.69 EUR in total in the French EUR bank account

1. What figure do I declare in revenue and state on my invoice for bookkeeping ( final EUR amount )?
2. On my invoice to client it was stated: TOTAL HT ESTIMATION EN EUROS (Taux de change du 24/07/2019 - Banque de France - 1 EUR = 0.8914 GBP) - but for bookkeeping do I change the Taux de change date to the day I received the payment in Transferwise GBP account or the day I received it in EUR in french bank account and change it to for example (Taux de change du 05/09/2019 - Transferwise - 1 EUR = 0.8995 GBP)?
3. I have received my first Declaration Mensuelle de Chiffre D’affaires from urssaf by post - do you have a guide on how I fill it up and how do I pay? There are 4 code de gestion from 054, 055, 792 to 576 for different activities with different taux en %. I work as a freelance art director/designer/animator and my Activite principale exercee APE was registered as 5911B Production de films institutionnels et publicitaires. Separately I also received a letter with Attestation d’exoneration Acre.

Thank you!!!