Welcome @demmy
Your website cannot be reached (times out) from everywhere except the Netherlands.
To use an HTTP Challenge (which the --nginx option uses) your site must be available world-wide. Let's Encrypt will check from various points around the globe.
An excellent wiki about this is here: Multi-Perspective Validation & Geoblocking FAQ
Here is results from a global testing site: Check website performance and response : Check host - online website monitoring