Google XML Sitemap plug ing for wordpress problem?

hello,

I have downloaded this plugin and it automatically submitted a sitemap to Google and Bing. Google Webmaster tool is showing me some strange crawling error (404). I mean by that that it shows urls that do not exist on my site. ex: one of the repeated error is https://www.barcelonelowcost/category/concert. I have no category on my blog, and concert is a tag??? it seems to me that there is a mess with the tags. Each post shows perfectly well on Internet and there is no category/tag mess in my blog wp dashboard.

So my question is, do i have to submit a sitemap manually and upload it directly on my webhosting? I do not know if i can do it a second time? If I submit it, i understand my webhosting will show 2 sitempas, no? how do I submit a sitemap to Google manually?

Thank you for your detailed answer (i am not a geek).

cheers,

Emmanuelle