Regarding B2C:
EDIT:
I just checkt: Odoo has a setting for EU-intra-community distance Selling.
- Go to Accounting > Configuration > Settings > Taxes
- Tick EU intra-community Distance Selling
The is a help article in the odoo docs under Finace > Accounting > Taxes
Best
Why would you use the VAT of the Country you are delivering too? AFIK (I am in Austria) and similar regulations apply to Germany, you use the Tax of the country where the service is provided. Therefore, your country.
B2B: Regulations for intra-Community acquisition (I hope this is the correct translation) apply.