@HistoPol
1) The reason why the tool is so slow is because of Mastodon's limit on how many posts you can request per second. I just did a quick test and the tool fetches 2k posts in about 1 minute and 40 seconds, so if my math is right, it could be up to 50 minutes total?
I recall someone suggesting I add settings for how many posts/how far back to go, so that might help, I just have to find the time for that.
2) This is all happening right in your browser, and all connections are directly between you and your server.
If you know how to use the network developer tool in your browser (https://support.iterable.com/hc/en-us/articles/115001674223-Developer-tools-in-Chrome-and-Firefox#network-tool), you can actually watch it make the requests, it will all go straight to mastodon.social.
The processed data is saved in your browser for an hour, so that you can refresh the page or come back within that time and still see the results without having to redo everything.