1 What type of weather station you have
Ambient Weather 2902A
2 Do you report your data to some other Internet website?
3 How technically do you send your reports to this other website. Which software or protocol do you use.
I use WeeWX and have added report generators for various service not included in the default package. Most (all?) are RESTful
4 Do you have any tips and ideas, how should our reporting API look like?
I do not, as I like the website and app as is. If PWS data is used, I'd leave it as a data source and not clutter the display with all the PWS sending data. Make it available of course, maybe a separate layer or display page.
5 Would you be willing to offer your station data to anyone else (not only windy.com) as open data?
Yes, of course. Data is a useful and valuable thing to many industries, such as the power industry.