I have come across a few options in the .de domain zone consisting of 10-11 characters. Although they are easy to write, they do not sound as appealing. This leads me to wonder if it is worth paying extra for domains in other zones like .com, .net, .info, etc. In the .net zone, I was able to find a short domain consisting of 6 characters that sounds good.

Are there any downsides to using .net that I should be aware of? Or is it best to stick with what is available in the .de domain? It seems like the keyword in the domain does not hold much significance nowadays.

My recommendation is to go with the .net domain zone. Based on your note, it appears that a name on this domain would be more memorable for potential visitors.
Even if it entails an extra cost, selecting .net is still a better option. In any case, the most crucial aspect is the content of the website itself since the domain zone plays a minor role in determining its ranking.

I would suggest purchasing a domain in the .com zone if your financial situation permits.
but, if you are unable to afford it, then registering in any other domain zone will suffice as it would not make any significant difference.

The .de domain is certainly popular in Germany and can carry a sense of trust among local audiences, but when it comes to global reach, .com or even .net might be better options.

One of the downsides of using a .net domain could be that it's often associated with networking and tech-related websites. This might not align with every type of business. If your website aims for a broader audience and is not tech-focused, users might find it a little confusing. Also, many people tend to assume that a website is a .com unless they're specifically searching for a .net, leading to potential loss of traffic as users may forget or mistype the domain.

On the other hand, the keyword relevance in a domain has diminished a lot over the years due to search engines changing their algorithms. While having a keyword in the domain can still provide some SEO benefits, factors like content quality, user experience, and backlinks have become much more critical. So if you can get a catchy or easy-to-remember .net domain, it could very well serve your purpose, especially if it contrasts the longer .de options you mentioned.

Moreover, consider your branding. A shorter and more memorable domain, like the 6-character .net option you found, could be more effective in creating a strong brand presence compared to a longer, less appealing .de variant.
Weigh out the pros and cons of both options. Think about your target audience and the image you want your brand to convey. If a snappy .net domain fits your branding better, it might be worth investing in it despite the possible drawbacks.