To change the currency in Odoo Community, go to Invoicing in the top navigation and then Settings in the left navigation. In the main area you will see the area Currencies. There you can choose between dollars and euros.
If you would like to have a different currency, then check the box in "Multiple currencies" and then click Activate other currency. In the newly opened window, you can then select and activate the new currency.
You change the taxes under „Invoicing > Accounting > Taxes". The first overview shows the current tax entries. It is important to know that the taxes in the basic setting are either related to the purchase or sale. To change the taxes, click on the respective entry and then change the tax code and the amount to the new tax amount (19%). After that you can save.
In order to then check whether the new taxes are effective, click on the side menu item "Settings" and check the entry in the Tax area.