I am currently testing ODOO 14 and would like to know how I can easily change the look of ODOO.

Especially the color and the typeface would be interesting, as well as it is possible to include a logo.

You can create your own theme or use any free themes from the odoo apps,

See: https://apps.odoo.com/apps/themes?price=Free

For creating new theme: https://www.odoo.com/documentation/14.0/howtos/themes.html

Steps to Install: How To Install Theme in Odoo