It isn't clear what the "General HTTP error" is from the screenshot you posted. I can access your site, robots.txt, and sitemap myself. To resolve that problem you should:
- Click on "1 instance" and try to see what specific error Googlebot is getting.
- Use "inspect URL" in Google Search Console with a live test to try and reproduce the problem
- Examine your server logs and see if there are errors.
It could be just a temporary error. If so, Googlebot will try again soon.
You can't force Google to index a site. It doesn't work that way. You can put a site up where Google can find it. If you make sure it can be crawled and make sure you have text content on each page, Google will usually want to index it. Even then, it could take months to see it data in Google Search Console.
Sitemaps have almost nothing to do with SEO. It is one way of letting Google know about the pages on your site, but it isn't the best way. Googlebot usually crawls all the URLs you put in a sitemap, however Google doesn't usually index URLs that are only found in a sitemap. Even if those URLs are indexed, they probably won't rank well without other help in the form of links to them. See The Sitemap Paradox.
The best way to get your site indexed and ranked is to:
- Look at your log files to make sure that Googlebot is crawling your site and you don't have too many error pages.
- Make sure every page has multiple links from other pages on your site.
- Get some external links to your site from your friends' and family's websites.
- Continue to build and promote your site over the next few weeks and months.