Hey professional, can you please help me How to apply German tax for all EU countries?

your tax rate (aka German tax) is based on Nexus. Nexus in NetSuite is set by country. to have German Rate applied to transactions you need to set your transactions “participants” (specifically, say, customers) to use German tax rate as default rate. The issue here is the way tax vendors are set in NS which is based, again, on Nexus which is based on country. So you will have to manually point out all that, an it is likely may involve a script in the end because you wont’ be able to change NS settings.